1.
Imperial unit
–
The system of imperial units or the imperial system is the system of units first defined in the British Weights and Measures Act of 1824, which was later refined and reduced. The Imperial units replaced the Winchester Standards, which were in effect from 1588 to 1825, the system came into official use across the British Empire. The imperial system developed from what were first known as English units, the Weights and Measures Act of 1824 was initially scheduled to go into effect on 1 May 1825. However, the Weights and Measures Act of 1825 pushed back the date to 1 January 1826, the 1824 Act allowed the continued use of pre-imperial units provided that they were customary, widely known, and clearly marked with imperial equivalents. Apothecaries units are mentioned neither in the act of 1824 nor 1825, at the time, apothecaries weights and measures were regulated in England, Wales, and Berwick-upon-Tweed by the London College of Physicians, and in Ireland by the Dublin College of Physicians. In Scotland, apothecaries units were unofficially regulated by the Edinburgh College of Physicians, the three colleges published, at infrequent intervals, pharmacopoeiae, the London and Dublin editions having the force of law. The Medical Act of 1858 transferred to The Crown the right to publish the official pharmacopoeia and to regulate apothecaries weights, Metric equivalents in this article usually assume the latest official definition. Before this date, the most precise measurement of the imperial Standard Yard was 0.914398416 metres, in 1824, the various different gallons in use in the British Empire were replaced by the imperial gallon, a unit close in volume to the ale gallon. It was originally defined as the volume of 10 pounds of distilled water weighed in air with brass weights with the standing at 30 inches of mercury at a temperature of 62 °F. The Weights and Measures Act of 1985 switched to a gallon of exactly 4.54609 l and these measurements were in use from 1826, when the new imperial gallon was defined, but were officially abolished in the United Kingdom on 1 January 1971. In the USA, though no longer recommended, the system is still used occasionally in medicine. The troy pound was made the unit of mass by the 1824 Act, however, its use was abolished in the UK on 1 January 1879, with only the troy ounce. The Weights and Measures Act 1855 made the pound the primary unit of mass. In all the systems, the unit is the pound. For the yard, the length of a pendulum beating seconds at the latitude of Greenwich at Mean Sea Level in vacuo was defined as 39.01393 inches, the imperial system is one of many systems of English units. Although most of the units are defined in more than one system, some units were used to a much greater extent, or for different purposes. The distinctions between these systems are not drawn precisely. One such distinction is that between these systems and older British/English units/systems or newer additions, the US customary system is historically derived from the English units that were in use at the time of settlement

Imperial unit
–
The former Weights and Measures office in

Seven Sisters, London.

Imperial unit
–
Imperial standards of length 1876 in

Trafalgar Square, London.

Imperial unit
–
A baby bottle that measures in three measurement systems—metric, imperial (UK), and US customary.

Imperial unit
–
A one US gallon gas can purchased near the US-Canada border. It shows equivalences in imperial gallons and litres.

2.
U.S. customary unit
–
United States customary units are a system of measurements commonly used in the United States. The United States customary system developed from English units which were in use in the British Empire before the US declared its independence, however, the British system of measures was overhauled in 1824 to create the imperial system, changing the definitions of some units. Therefore, while many U. S. units are similar to their Imperial counterparts. The majority of U. S. customary units were redefined in terms of the meter and these definitions were refined by the international yard and pound agreement of 1959. Americans primarily use customary units in commercial activities, as well as for personal and social use, in science, medicine, many sectors of industry and some of government, metric units are used. The International System of Units, the form of the metric system, is preferred for many uses by the U. S. National Institute of Standards. The United States system of units is similar to the British imperial system, both systems are derived from English units, a system which had evolved over the millennia before American independence, and which had its roots in Roman and Anglo-Saxon units. The customary system was championed by the U. S. -based International Institute for Preserving and Perfecting Weights, advocates of the customary system saw the French Revolutionary, or metric, system as atheistic. An auxiliary of the Institute in Ohio published a poem with wording such as down with every metric scheme and A perfect inch, one adherent of the customary system called it a just weight and a just measure, which alone are acceptable to the Lord. The U. S. government passed the Metric Conversion Act of 1975, the legislation states that the federal government has a responsibility to assist industry as it voluntarily converts to the metric system, i. e. metrification. This is most evident in U. S. labeling requirements on food products, according to the CIA Factbook, the United States is one of three nations that have not adopted the metric system as their official system of weights and measures. U. S. customary units are used on consumer products. Metric units are standard in science, medicine, as well as many sectors of industry and government, the metric system also lacks a parallel to the foot. Frequently, however, these units designate quite different sizes, for example, the mile ranged by country from one-half to five U. S. miles, foot and pound also had varying definitions. Historically, a range of non-SI units were used in the U. S. and in Britain. This article deals only with the commonly used or officially defined in the U. S. For measuring length, the U. S. customary system uses the inch, foot, yard, and mile, since July 1,1959, these have been defined on the basis of 1 yard =0.9144 meters except for some applications in surveying. The U. S. the United Kingdom and other Commonwealth countries agreed on this definition, the NAD27 was replaced in the 1980s by the North American Datum of 1983, which is defined in meters

U.S. customary unit
–
A 23.7 US fl oz (700 ml) bottle displaying both US and metric units.

3.
Metric system
–
The metric system is an internationally agreed decimal system of measurement. Many sources also cite Liberia and Myanmar as the other countries not to have done so. Although the originators intended to devise a system that was accessible to all. Control of the units of measure was maintained by the French government until 1875, when it was passed to an intergovernmental organisation. From its beginning, the features of the metric system were the standard set of interrelated base units. These base units are used to larger and smaller units that could replace a huge number of other units of measure in existence. Although the system was first developed for use, the development of coherent units of measure made it particularly suitable for science. Although the metric system has changed and developed since its inception, designed for transnational use, it consisted of a basic set of units of measurement, now known as base units. At the outbreak of the French Revolution in 1789, most countries, the metric system was designed to be universal—in the words of the French philosopher Marquis de Condorcet it was to be for all people for all time. However, these overtures failed and the custody of the metric system remained in the hands of the French government until 1875. In languages where the distinction is made, unit names are common nouns, the concept of using consistent classical names for the prefixes was first proposed in a report by the Commission on Weights and Measures in May 1793. The prefix kilo, for example, is used to multiply the unit by 1000, thus the kilogram and kilometre are a thousand grams and metres respectively, and a milligram and millimetre are one thousandth of a gram and metre respectively. These relations can be written symbolically as,1 mg =0, however,1935 extensions to the prefix system did not follow this convention, the prefixes nano- and micro-, for example have Greek roots. During the 19th century the prefix myria-, derived from the Greek word μύριοι, was used as a multiplier for 10000, prefixes are not usually used to indicate multiples of a second greater than 1, the non-SI units of minute, hour and day are used instead. On the other hand, prefixes are used for multiples of the unit of volume. The base units used in the system must be realisable. Each of the units in SI is accompanied by a mise en pratique published by the BIPM that describes in detail at least one way in which the base unit can be measured. In practice, such realisation is done under the auspices of a mutual acceptance arrangement, in the original version of the metric system the base units could be derived from a specified length and the weight of a specified volume of pure water

Metric system
–
"The metric system is for all people for all time." (

Condorcet, 1791). Four everyday measuring devices that have metric calibrations: a

tape measure calibrated in

centimetres, a

thermometer calibrated in

degrees Celsius, a

kilogram weight, and an electrical

multimeter that measures

volts,

amperes and

ohms.

Metric system
–
Countries which have officially adopted the metric system

Metric system
–
Chinese road sign listing distances on an

expressway in eastern Beijing. Although the primary text is in Chinese, the distances use internationally recognised characters.

Metric system
–

James Clerk Maxwell played a major role in developing the concept of a coherent CGS system and in extending the metric system to include electrical units.

4.
Area
–
Area is the quantity that expresses the extent of a two-dimensional figure or shape, or planar lamina, in the plane. Surface area is its analog on the surface of a three-dimensional object. It is the analog of the length of a curve or the volume of a solid. The area of a shape can be measured by comparing the shape to squares of a fixed size, in the International System of Units, the standard unit of area is the square metre, which is the area of a square whose sides are one metre long. A shape with an area of three square metres would have the area as three such squares. In mathematics, the square is defined to have area one. There are several formulas for the areas of simple shapes such as triangles, rectangles. Using these formulas, the area of any polygon can be found by dividing the polygon into triangles, for shapes with curved boundary, calculus is usually required to compute the area. Indeed, the problem of determining the area of plane figures was a motivation for the historical development of calculus. For a solid such as a sphere, cone, or cylinder. Formulas for the areas of simple shapes were computed by the ancient Greeks. Area plays an important role in modern mathematics, in addition to its obvious importance in geometry and calculus, area is related to the definition of determinants in linear algebra, and is a basic property of surfaces in differential geometry. In analysis, the area of a subset of the plane is defined using Lebesgue measure, in general, area in higher mathematics is seen as a special case of volume for two-dimensional regions. Area can be defined through the use of axioms, defining it as a function of a collection of certain plane figures to the set of real numbers and it can be proved that such a function exists. An approach to defining what is meant by area is through axioms, area can be defined as a function from a collection M of special kind of plane figures to the set of real numbers which satisfies the following properties, For all S in M, a ≥0. If S and T are in M then so are S ∪ T and S ∩ T, if S and T are in M with S ⊆ T then T − S is in M and a = a − a. If a set S is in M and S is congruent to T then T is also in M, every rectangle R is in M. If the rectangle has length h and breadth k then a = hk, let Q be a set enclosed between two step regions S and T

Area
–
A square metre

quadrat made of PVC pipe.

Area
–
The combined area of these three

shapes is

approximately 15.57

squares.

5.
Square (geometry)
–
In geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles. It can also be defined as a rectangle in which two adjacent sides have equal length, a square with vertices ABCD would be denoted ◻ ABCD. e. A rhombus with equal diagonals a convex quadrilateral with sides a, b, c, d whose area is A =12 =12. Opposite sides of a square are both parallel and equal in length, all four angles of a square are equal. All four sides of a square are equal, the diagonals of a square are equal. The square is the n=2 case of the families of n-hypercubes and n-orthoplexes, a truncated square, t, is an octagon. An alternated square, h, is a digon, the perimeter of a square whose four sides have length ℓ is P =4 ℓ and the area A is A = ℓ2. In classical times, the power was described in terms of the area of a square. This led to the use of the square to mean raising to the second power. The area can also be calculated using the diagonal d according to A = d 22. In terms of the circumradius R, the area of a square is A =2 R2, since the area of the circle is π R2, in terms of the inradius r, the area of the square is A =4 r 2. Because it is a polygon, a square is the quadrilateral of least perimeter enclosing a given area. Dually, a square is the quadrilateral containing the largest area within a given perimeter. Indeed, if A and P are the area and perimeter enclosed by a quadrilateral, then the isoperimetric inequality holds,16 A ≤ P2 with equality if. The diagonals of a square are 2 times the length of a side of the square and this value, known as the square root of 2 or Pythagoras constant, was the first number proven to be irrational. A square can also be defined as a parallelogram with equal diagonals that bisect the angles, if a figure is both a rectangle and a rhombus, then it is a square. If a circle is circumscribed around a square, the area of the circle is π /2 times the area of the square, if a circle is inscribed in the square, the area of the circle is π /4 times the area of the square. A square has an area than any other quadrilateral with the same perimeter

Square (geometry)
–
A regular

quadrilateral (tetragon)

6.
Foot (length)
–
The foot is a unit of length in the imperial and US customary systems of measurement. Since 1959, both units have been defined by international agreement as equivalent to 0.3048 meters exactly, in both systems, the foot comprises 12 inches and three feet compose a yard. Historically the foot was a part of local systems of units, including the Greek, Roman, Chinese, French. It varied in length from country to country, from city to city and its length was usually between 250 mm and 335 mm and was generally, but not always, subdivided into 12 inches or 16 digits. The United States is the industrialized nation that uses the international foot and the survey foot in preference to the meter in its commercial, engineering. The foot is legally recognized in the United Kingdom, road signs must use imperial units, the measurement of altitude in international aviation is one of the few areas where the foot is widely used outside the English-speaking world. The length of the international foot corresponds to a foot with shoe size of 13,14,15.5 or 46. Historically the human body has been used to provide the basis for units of length. The foot of a male is typically about 15. 3% of his height, giving a person of 160 cm a foot of 245 mm. These figures are less than the used in most cities over time. Archeologists believe that the Egyptians, Ancient Indians and Mesopotamians preferred the cubit while the Romans, under the Harappan linear measures, Indus cities during the Bronze Age used a foot of 13.2 inches and a cubit of 20.8 inches. The Egyptian equivalent of the measure of four palms or 16 digits—was known as the djeser and has been reconstructed as about 30 cm. The Greek foot had a length of 1⁄600 of a stadion, one stadion being about 181.2 m, the standard Roman foot was normally about 295.7 mm, but in the provinces, the pes Drusianus was used, with a length of about 334 mm. Originally both the Greeks and the Romans subdivided the foot into 16 digits, but in later years, after the fall of the Roman Empire, some Roman traditions were continued but others fell into disuse. In AD790 Charlemagne attempted to reform the units of measure in his domains and his units of length were based on the toise and in particular the toise de lÉcritoire, the distance between the fingertips of the outstretched arms of a man. The toise has 6 pieds each of 326.6 mm, at the same time, monastic buildings used the Carolingian foot of 340 mm. The procedure for verification of the foot as described in the 16th century by Jacob Koebel in his book Geometrei, the measures of Iron Age Britain are uncertain and proposed reconstructions such as the Megalithic Yard are controversial. Later Welsh legend credited Dyfnwal Moelmud with the establishment of their units, the Belgic or North German foot of 335 mm was introduced to England either by the Belgic Celts during their invasions prior to the Romans or by the Anglo-Saxons in the 5th & 6th century

Foot (length)
–
The unofficial public

imperial measurement standards erected at the

Royal Observatory in

Greenwich in the 19th century

Foot (length)
–
Determination of the rod, using the length of the left foot of 16 randomly chosen people coming from church service. Woodcut published in the book Geometrei by Jakob Köbel (Frankfurt, c. 1536).

Foot (length)
–
Page from Austrian Lehrbuch des gesammten Rechnens für die vierte Classe der Hauptschulen in den k.k. Staaten – 1848

7.
Architecture
–
Architecture is both the process and the product of planning, designing, and constructing buildings and other physical structures. Architectural works, in the form of buildings, are often perceived as cultural symbols. Historical civilizations are often identified with their surviving architectural achievements, Architecture can mean, A general term to describe buildings and other physical structures. The art and science of designing buildings and nonbuilding structures, the style of design and method of construction of buildings and other physical structures. A unifying or coherent form or structure Knowledge of art, science, technology, the design activity of the architect, from the macro-level to the micro-level. The practice of the architect, where architecture means offering or rendering services in connection with the design and construction of buildings. The earliest surviving work on the subject of architecture is De architectura. According to Vitruvius, a building should satisfy the three principles of firmitas, utilitas, venustas, commonly known by the original translation – firmness, commodity. An equivalent in modern English would be, Durability – a building should stand up robustly, utility – it should be suitable for the purposes for which it is used. Beauty – it should be aesthetically pleasing, according to Vitruvius, the architect should strive to fulfill each of these three attributes as well as possible. Leon Battista Alberti, who elaborates on the ideas of Vitruvius in his treatise, De Re Aedificatoria, saw beauty primarily as a matter of proportion, for Alberti, the rules of proportion were those that governed the idealised human figure, the Golden mean. The most important aspect of beauty was, therefore, an inherent part of an object, rather than something applied superficially, Gothic architecture, Pugin believed, was the only true Christian form of architecture. The 19th-century English art critic, John Ruskin, in his Seven Lamps of Architecture, Architecture was the art which so disposes and adorns the edifices raised by men. That the sight of them contributes to his health, power. For Ruskin, the aesthetic was of overriding significance and his work goes on to state that a building is not truly a work of architecture unless it is in some way adorned. For Ruskin, a well-constructed, well-proportioned, functional building needed string courses or rustication, but suddenly you touch my heart, you do me good. I am happy and I say, This is beautiful, le Corbusiers contemporary Ludwig Mies van der Rohe said Architecture starts when you carefully put two bricks together. The notable 19th-century architect of skyscrapers, Louis Sullivan, promoted an overriding precept to architectural design, function came to be seen as encompassing all criteria of the use, perception and enjoyment of a building, not only practical but also aesthetic, psychological and cultural

Architecture
–

Brunelleschi, in the building of the dome of

Florence Cathedral in the early 15th-century, not only transformed the building and the city, but also the role and status of the architect.

Architecture
–
Section of

Brunelleschi 's dome drawn by the architect

Cigoli (c. 1600)

Architecture
–
The

Parthenon,

Athens,

Greece, "the supreme example among architectural sites."

(Fletcher).

Architecture
–
The

Houses of Parliament, Westminster, master-planned by

Charles Barry, with interiors and details by A.W.N. Pugin

8.
Real estate
–
Also, the business of real estate, the profession of buying, selling, or renting land, buildings or housing. It is a term used in jurisdictions whose legal system is derived from English common law, such as India, the United Kingdom, United States, Canada, Pakistan, Australia. Residential real estate may contain either a family or multifamily structure. Residences can be classified by, if, and how they are connected to neighbouring residences, different types of housing tenure can be used for the same physical type. For example, connected residents might be owned by an entity and leased out. Major categories in North America and Europe Attached / multi-unit dwellings Apartment or Flat – An individual unit in a multi-unit building, the boundaries of the apartment are generally defined by a perimeter of locked or lockable doors. Often seen in apartment buildings. Multi-family house – Often seen in multi-story detached buildings, where each floor is an apartment or unit. Terraced house – A number of single or multi-unit buildings in a row with shared walls. Condominium – Building or complex, similar to apartments, owned by individuals, common grounds and common areas within the complex are owned and shared jointly. There are townhouse or rowhouse style condominiums as well, semi-detached dwellings Duplex – Two units with one shared wall. Single-family detached house Portable dwellings Mobile homes – Potentially a full-time residence which can be movable on wheels, houseboats – A floating home Tents – Usually very temporary, with roof and walls consisting only of fabric-like material. The size of an apartment or house can be described in square feet or meters, in the United States, this includes the area of living space, excluding the garage and other non-living spaces. It can be described roughly by the number of rooms. A studio apartment has a bedroom with no living room. A one-bedroom apartment has a living or dining room separate from the bedroom, Two bedroom, three bedroom, and larger units are common. Major categories in India and the Asian Subcontinent Co-operative Housing Societies Condominiums Chawls Villas Havelis The size is measured in Gaz, Quila, Marla, Beegha, and acre. See List of house types for a listing of housing types and layouts, real estate trends for shifts in the market

Real estate
–
'Single-family detached house'

9.
Floor plans
–
Dimensions are usually drawn between the walls to specify room sizes and wall lengths. Floor plans may also include details of fixtures like sinks, water heaters, furnaces, floor plans may include notes for construction to specify finishes, construction methods, or symbols for electrical items. Similar to a map the orientation of the view is downward from above, but unlike a conventional map, objects below this level are seen, objects at this level are shown cut in plan-section, and objects above this vertical position within the structure are omitted or shown dashed. Plan view or planform is defined as an orthographic projection of an object on a horizontal plane. The term may be used in general to any drawing showing the physical layout of objects. For example, it may denote the arrangement of the objects at an exhibition. Drawings are now reproduced using plotters and large format xerographic copiers and this convention maintains the same orientation of the floor and ceilings plans - looking down from above. RCPs are used by designers and architects to demonstrate lighting, visible mechanical features, a floor plan is not a top view or birds eye view. It is a drawing to scale of the layout of a floor in a building. A top view or birds eye view does not show an orthogonally projected plane cut at the typical 4 foot height above the floor level, a floor plan could show, Interior walls and hallways Restrooms Windows and doors Appliances such as stoves, refrigerators, water heater etc. In other words, a plan is a section viewed from the top, in such views, the portion of the object above the plane is omitted to reveal what lies beyond. In the case of a plan, the roof and upper portion of the walls may typically be omitted. Roof plans are orthographic projections, but they are not sections as their plane is outside of the object. A plan is a method of depicting the internal arrangement of a 3-dimensional object in two dimensions. It is often used in drawing and is traditionally crosshatched. The style of crosshatching indicates the type of material the section passes through, a 3D floor plan can be defined as a virtual model of a building floor plan. Its often used to better convey architectural plans to individuals not familiar with floor plans, despite the purpose of floor plans originally being to depict 3D layouts in a 2D manner, technological expansion has made rendering 3D models much more cost effective. 3D plans show a depth of image and are often complimented by 3D furniture in the room

Floor plans
–
Sample floor plan for a

single-family detached home
10.
Acre
–
The acre is a unit of land area used in the imperial and US customary systems. It is defined as the area of 1 chain by 1 furlong, lucia, St. Helena, St. Kitts and Nevis, St. Vincent and the Grenadines, Turks and Caicos, the United Kingdom, the United States and the US Virgin Islands. The international symbol of the acre is ac, the most commonly used acre today is the international acre. In the United States both the international acre and the US survey acre are in use, but differ by two parts per million, see below. The most common use of the acre is to measure tracts of land, one international acre is defined as exactly 4,046.8564224 square metres. An acre was defined in the Middle Ages, being the amount of land that could be ploughed in one day with a yoke of oxen. One acre equals 0.0015625 square miles,4,840 square yards,43,560 square feet or about 4,047 square metres. While all modern variants of the acre contain 4,840 square yards, there are definitions of a yard. A square enclosing one acre is approximately 69.57 yards, as a unit of measure, an acre has no prescribed shape, any area of 43,560 square feet is an acre. In the international yard and pound agreement of 1959 the United States, consequently, the international acre is exactly 4,046.8564224 square metres. The US survey acre is about 4,046.872609874252 square metres, its value is based on an inch defined by 1 metre =39.37 inches exactly. Surveyors in the United States use both international and survey feet, and consequently, both varieties of acre. Since the difference between the US survey acre and international acre is only about a quarter of the size of an A4 sheet of paper, areas are seldom measured with sufficient accuracy for the different definitions to be detectable. In India, residential plots are measured in cents or decimal, in Sri Lanka the division of an acre into 160 perches or 4 roods is common. To be more exact, one acre is 90.75 percent of a 100 yards long by 53.33 yards wide American football field, the full field, including the end zones, covers approximately 1.32 acres. For residents of countries, the acre might be envisaged as approximately half of a 105 metres long by 68 metres wide association football pitch. It may also be remembered as 44,000 square feet, in English it was historically spelled aker. The acre was approximately the amount of land tillable by a yoke of oxen in one day and this explains one definition as the area of a rectangle with sides of length one chain and one furlong

Acre
–
Comparison of 1 Acre with some Imperial and metric units of area

11.
Area (geometry)
–
Area is the quantity that expresses the extent of a two-dimensional figure or shape, or planar lamina, in the plane. Surface area is its analog on the surface of a three-dimensional object. It is the analog of the length of a curve or the volume of a solid. The area of a shape can be measured by comparing the shape to squares of a fixed size, in the International System of Units, the standard unit of area is the square metre, which is the area of a square whose sides are one metre long. A shape with an area of three square metres would have the area as three such squares. In mathematics, the square is defined to have area one. There are several formulas for the areas of simple shapes such as triangles, rectangles. Using these formulas, the area of any polygon can be found by dividing the polygon into triangles, for shapes with curved boundary, calculus is usually required to compute the area. Indeed, the problem of determining the area of plane figures was a motivation for the historical development of calculus. For a solid such as a sphere, cone, or cylinder. Formulas for the areas of simple shapes were computed by the ancient Greeks. Area plays an important role in modern mathematics, in addition to its obvious importance in geometry and calculus, area is related to the definition of determinants in linear algebra, and is a basic property of surfaces in differential geometry. In analysis, the area of a subset of the plane is defined using Lebesgue measure, in general, area in higher mathematics is seen as a special case of volume for two-dimensional regions. Area can be defined through the use of axioms, defining it as a function of a collection of certain plane figures to the set of real numbers and it can be proved that such a function exists. An approach to defining what is meant by area is through axioms, area can be defined as a function from a collection M of special kind of plane figures to the set of real numbers which satisfies the following properties, For all S in M, a ≥0. If S and T are in M then so are S ∪ T and S ∩ T, if S and T are in M with S ⊆ T then T − S is in M and a = a − a. If a set S is in M and S is congruent to T then T is also in M, every rectangle R is in M. If the rectangle has length h and breadth k then a = hk, let Q be a set enclosed between two step regions S and T

Area (geometry)
–
A square metre

quadrat made of PVC pipe.

Area (geometry)
–
The combined area of these three

shapes is

approximately 15.57

squares.

12.
Conversion of units
–
Conversion of units is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors. The process of conversion depends on the situation and the intended purpose. This may be governed by regulation, contract, technical specifications or other published standards, engineering judgment may include such factors as, The precision and accuracy of measurement and the associated uncertainty of measurement. The statistical confidence interval or tolerance interval of the initial measurement, the number of significant figures of the measurement. The intended use of the measurement including the engineering tolerances, historical definitions of the units and their derivatives used in old measurements, e. g. international foot vs. Some conversions from one system of units to another need to be exact and this is sometimes called soft conversion. It does not involve changing the configuration of the item being measured. By contrast, a conversion or an adaptive conversion may not be exactly equivalent. It changes the measurement to convenient and workable numbers and units in the new system and it sometimes involves a slightly different configuration, or size substitution, of the item. Nominal values are allowed and used. A conversion factor is used to change the units of a quantity without changing its value. The unity bracket method of unit conversion consists of a fraction in which the denominator is equal to the numerator, because of the identity property of multiplication, the value of a number will not change as long as it is multiplied by one. Also, if the numerator and denominator of a fraction are equal to each other, so as long as the numerator and denominator of the fraction are equivalent, they will not affect the value of the measured quantity. There are many applications that offer the thousands of the various units with conversions. For example, the free software movement offers a command line utility GNU units for Linux and this article gives lists of conversion factors for each of a number of physical quantities, which are listed in the index. For each physical quantity, a number of different units are shown, Conversion between units in the metric system can be discerned by their prefixes and are thus not listed in this article. Exceptions are made if the unit is known by another name. Within each table, the units are listed alphabetically, and the SI units are highlighted, notes, See Weight for detail of mass/weight distinction and conversion

Conversion of units
–

Base units
13.
Metrication in Canada
–
Until the 1970s, Canada traditionally used the Imperial measurement system, labelled as Canadian units of measurements under Schedule II, Section 4 of the Weights and Measures Act. These units have the name and, with the exception of capacity measures such as the gallon. For example, before metrication in Canada, gasoline was sold by the imperial gallon, in cross-border transactions, it was often unclear whether values quoted in gallons, etc. were referring to the US values or the imperial values of these units. By the mid-1970s, metric product labelling was introduced, in 1972, the provinces agreed to make all road signs metric by 1977. There was some resistance to metrication, especially as the sectors of the economy where the federal Weights, the city of Peterborough, Ontario, was a noted hotbed of opposition to metrication, having been one of the governments three test centres for the metrication process. Bill Domm, a Member of Parliament representing the riding of Peterborough, was one of the countrys most outspoken opponents of metrication, during this period, a few government employees lost their jobs for their opposition to metrication. Neil Fraser, an official with Revenue Canada who publicly opposed mandatory metric conversion, was dismissed for conduct unacceptable for a public servant. Since 1976, the law requires that all prepackaged food products must declare their mass or their volume in metric units, milk has been thoroughly metric since 1980. In April 1975, Fahrenheit temperatures were replaced by Celsius, in September 1975, rainfall was first measured in millimetres and snow in centimetres. Since April 1976, wind speed, visibility, and barometric pressure have been in SI units, in September 1977, every speed-limit sign in the country was changed from miles per hour to kilometres per hour. The election of the Progressive Conservative government of Brian Mulroney in 1984 resulted in the abolition of the Metric Commission on March 31,1985 and this ended the process of affirmative metrication in Canada, and some regulations requiring metric measurements either have been repealed or are no longer enforced. Training on metric conversion was not universal, poor metrication training was a contributing factor to Air Canada Flight 143, the so-called Gimli Glider, running out of fuel mid-flight on 23 July 1983. Notwithstanding the end of officially sanctioned metrication in Canada, most laws, regulations, however, imperial measures still have legal definitions in Canada and can be used alongside metric units. Cars have metric speedometers and odometers, although some speedometers include smaller figures in miles per hour, fuel efficiency for new vehicles is published by Natural Resources Canada in litres per 100 kilometres and miles per gallon. Window stickers in dealer showrooms often include miles per gallon conversions, the railways of Canada continue to measure their trackage in miles, and speed limits in mph. Canadian railcars show weight figures in both imperial and metric, today, Canadians typically use a mix of metric and imperial measurements in their daily lives. However the use of the metric and imperial systems varies according to generations, newborns are measured in SI at hospitals, but the birth weight and length is also announced to family and friends in imperial units. Among the broader population, imperial units are sometimes used to indicate height and weight

Metrication in Canada
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A long-ago metricated speed-limit sign in

Bolton, Ontario, with the old "25 mph" value now showing through

Metrication in Canada
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The metrication logo used in Canada during the 1970s and 1980s.

14.
Square (algebra)
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In mathematics, a square is the result of multiplying a number by itself. The verb to square is used to denote this operation, squaring is the same as raising to the power 2, and is denoted by a superscript 2, for instance, the square of 3 may be written as 32, which is the number 9. In some cases when superscripts are not available, as for instance in programming languages or plain text files, the adjective which corresponds to squaring is quadratic. The square of an integer may also be called a number or a perfect square. In algebra, the operation of squaring is often generalized to polynomials, other expressions, for instance, the square of the linear polynomial x +1 is the quadratic polynomial x2 + 2x +1. One of the important properties of squaring, for numbers as well as in other mathematical systems, is that. That is, the function satisfies the identity x2 =2. This can also be expressed by saying that the function is an even function. The squaring function preserves the order of numbers, larger numbers have larger squares. In other words, squaring is a function on the interval. Hence, zero is its global minimum, the only cases where the square x2 of a number is less than x occur when 0 < x <1, that is, when x belongs to an open interval. This implies that the square of an integer is never less than the original number, every positive real number is the square of exactly two numbers, one of which is strictly positive and the other of which is strictly negative. Zero is the square of one number, itself. For this reason, it is possible to define the square root function, no square root can be taken of a negative number within the system of real numbers, because squares of all real numbers are non-negative. There are several uses of the squaring function in geometry. The name of the squaring function shows its importance in the definition of the area, the area depends quadratically on the size, the area of a shape n times larger is n2 times greater. The squaring function is related to distance through the Pythagorean theorem and its generalization, Euclidean distance is not a smooth function, the three-dimensional graph of distance from a fixed point forms a cone, with a non-smooth point at the tip of the cone. However, the square of the distance, which has a paraboloid as its graph, is a smooth, the dot product of a Euclidean vector with itself is equal to the square of its length, v⋅v = v2

Square (algebra)
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The

composition of the tiling

Image:ConformId.jpg (understood as a function on the complex plane) with the complex square function

Square (algebra)
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5⋅5, or 5 2 (5 squared), can be shown graphically using a

square. Each block represents one unit, 1⋅1, and the entire square represents 5⋅5, or the area of the square.

15.
Square root
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In mathematics, a square root of a number a is a number y such that y2 = a, in other words, a number y whose square is a. For example,4 and −4 are square roots of 16 because 42 =2 =16, every nonnegative real number a has a unique nonnegative square root, called the principal square root, which is denoted by √a, where √ is called the radical sign or radix. For example, the square root of 9 is 3, denoted √9 =3. The term whose root is being considered is known as the radicand, the radicand is the number or expression underneath the radical sign, in this example 9. Every positive number a has two roots, √a, which is positive, and −√a, which is negative. Together, these two roots are denoted ± √a, although the principal square root of a positive number is only one of its two square roots, the designation the square root is often used to refer to the principal square root. For positive a, the square root can also be written in exponent notation. Square roots of numbers can be discussed within the framework of complex numbers. In Ancient India, the knowledge of theoretical and applied aspects of square and square root was at least as old as the Sulba Sutras, a method for finding very good approximations to the square roots of 2 and 3 are given in the Baudhayana Sulba Sutra. Aryabhata in the Aryabhatiya, has given a method for finding the root of numbers having many digits. It was known to the ancient Greeks that square roots of positive numbers that are not perfect squares are always irrational numbers, numbers not expressible as a ratio of two integers. This is the theorem Euclid X,9 almost certainly due to Theaetetus dating back to circa 380 BC, the particular case √2 is assumed to date back earlier to the Pythagoreans and is traditionally attributed to Hippasus. Mahāvīra, a 9th-century Indian mathematician, was the first to state that square roots of negative numbers do not exist, a symbol for square roots, written as an elaborate R, was invented by Regiomontanus. An R was also used for Radix to indicate square roots in Gerolamo Cardanos Ars Magna, according to historian of mathematics D. E. Smith, Aryabhatas method for finding the root was first introduced in Europe by Cataneo in 1546. According to Jeffrey A. Oaks, Arabs used the letter jīm/ĝīm, the letter jīm resembles the present square root shape. Its usage goes as far as the end of the century in the works of the Moroccan mathematician Ibn al-Yasamin. The symbol √ for the root was first used in print in 1525 in Christoph Rudolffs Coss

Square root
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First leaf of the complex square root

Square root
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The mathematical expression 'The (principal) square root of x"