Manufacturing is the production of products for use or sale using labour and machines, tools and biological processing, or formulation. The term may refer to a range of human activity, from handicraft to high tech, but is most applied to industrial design, in which raw materials are transformed into finished goods on a large scale; such finished goods may be sold to other manufacturers for the production of other, more complex products, such as aircraft, household appliances, sports equipment or automobiles, or sold to wholesalers, who in turn sell them to retailers, who sell them to end users and consumers. Manufacturing engineering or manufacturing process are the steps through which raw materials are transformed into a final product; the manufacturing process begins with the product design, materials specification from which the product is made. These materials are modified through manufacturing processes to become the required part. Modern manufacturing includes all intermediate processes required in the production and integration of a product's components.
Some industries, such as semiconductor and steel manufacturers use the term fabrication instead. The manufacturing sector is connected with engineering and industrial design. Examples of major manufacturers in North America include General Motors Corporation, General Electric, Procter & Gamble, General Dynamics, Boeing and Precision Castparts. Examples in Europe include Volkswagen Siemens, FCA and Michelin. Examples in Asia include Toyota, Panasonic, LG, Samsung and Tata Motors. In its earliest form, manufacturing was carried out by a single skilled artisan with assistants. Training was by apprenticeship. In much of the pre-industrial world, the guild system protected the privileges and trade secrets of urban artisans. Before the Industrial Revolution, most manufacturing occurred in rural areas, where household-based manufacturing served as a supplemental subsistence strategy to agriculture. Entrepreneurs organized a number of manufacturing households into a single enterprise through the putting-out system.
Toll manufacturing is an arrangement whereby a first firm with specialized equipment processes raw materials or semi-finished goods for a second firm. Manufacturing Engineering Agile manufacturing American system of manufacturing British factory system of manufacturing Craft or guild system Fabrication Flexible manufacturing Just-in-time manufacturing Lean manufacturing Mass customization – 3D printing, design-your-own web sites for sneakers, fast fashion Mass production Ownership Packaging and labeling Prefabrication Putting-out system Rapid manufacturing Reconfigurable manufacturing system Soviet collectivism in manufacturing History of numerical control Emerging technologies have provided some new growth in advanced manufacturing employment opportunities in the Manufacturing Belt in the United States. Manufacturing provides important material support for national infrastructure and for national defense. On the other hand, most manufacturing may involve significant environmental costs; the clean-up costs of hazardous waste, for example, may outweigh the benefits of a product that creates it.
Hazardous materials may expose workers to health risks. These costs are now well known and there is effort to address them by improving efficiency, reducing waste, using industrial symbiosis, eliminating harmful chemicals; the negative costs of manufacturing can be addressed legally. Developed countries regulate manufacturing activity with environmental laws. Across the globe, manufacturers can be subject to regulations and pollution taxes to offset the environmental costs of manufacturing activities. Labor unions and craft guilds have played a historic role in the negotiation of worker rights and wages. Environment laws and labor protections that are available in developed nations may not be available in the third world. Tort law and product liability impose additional costs on manufacturing; these are significant dynamics in the ongoing process, occurring over the last few decades, of manufacture-based industries relocating operations to "developing-world" economies where the costs of production are lower than in "developed-world" economies.
Manufacturing has unique health and safety challenges and has been recognized by the National Institute for Occupational Safety and Health as a priority industry sector in the National Occupational Research Agenda to identify and provide intervention strategies regarding occupational health and safety issues. Surveys and analyses of trends and issues in manufacturing and investment around the world focus on such things as: The nature and sources of the considerable variations that occur cross-nationally in levels of manufacturing and wider industrial-economic growth. In addition to general overviews, researchers have examined the features and factors affecting particular key aspects of manufacturing development, they have compared production and investment in a range of Western and non-Western countries and presented case studies of growth and performance in important individual industries and market-economic sectors. On June 26, 2009, Jeff Immelt, the CEO of General Electric, called for the United States to increase its manufacturing base employment to 20% of the workforce, commenting that the U.
S. has outsourced too much in some areas and can no longer rely on the financial sector and consumer spending to drive demand. Further, while U. S. manufacturing performs well compared to the rest of the U. S. economy, research shows that it performs poorly compared to manufacturing in other high-wage countries. A total of 3.2 million – one in six U. S. manuf
Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe. The earliest roots of science can be traced to Ancient Egypt and Mesopotamia in around 3500 to 3000 BCE, their contributions to mathematics and medicine entered and shaped Greek natural philosophy of classical antiquity, whereby formal attempts were made to explain events of the physical world based on natural causes. After the fall of the Western Roman Empire, knowledge of Greek conceptions of the world deteriorated in Western Europe during the early centuries of the Middle Ages but was preserved in the Muslim world during the Islamic Golden Age; the recovery and assimilation of Greek works and Islamic inquiries into Western Europe from the 10th to 13th century revived natural philosophy, transformed by the Scientific Revolution that began in the 16th century as new ideas and discoveries departed from previous Greek conceptions and traditions. The scientific method soon played a greater role in knowledge creation and it was not until the 19th century that many of the institutional and professional features of science began to take shape.
Modern science is divided into three major branches that consist of the natural sciences, which study nature in the broadest sense. There is disagreement, however, on whether the formal sciences constitute a science as they do not rely on empirical evidence. Disciplines that use existing scientific knowledge for practical purposes, such as engineering and medicine, are described as applied sciences. Science is based on research, conducted in academic and research institutions as well as in government agencies and companies; the practical impact of scientific research has led to the emergence of science policies that seek to influence the scientific enterprise by prioritizing the development of commercial products, health care, environmental protection. Science in a broad sense existed in many historical civilizations. Modern science is distinct in its approach and successful in its results, so it now defines what science is in the strictest sense of the term. Science in its original sense was a word for a type of knowledge, rather than a specialized word for the pursuit of such knowledge.
In particular, it was the type of knowledge which people can communicate to share. For example, knowledge about the working of natural things was gathered long before recorded history and led to the development of complex abstract thought; this is shown by the construction of complex calendars, techniques for making poisonous plants edible, public works at national scale, such as those which harnessed the floodplain of the Yangtse with reservoirs and dikes, buildings such as the Pyramids. However, no consistent conscious distinction was made between knowledge of such things, which are true in every community, other types of communal knowledge, such as mythologies and legal systems. Metallurgy was known in prehistory, the Vinča culture was the earliest known producer of bronze-like alloys, it is thought that early experimentation with heating and mixing of substances over time developed into alchemy. Neither the words nor the concepts "science" and "nature" were part of the conceptual landscape in the ancient near east.
The ancient Mesopotamians used knowledge about the properties of various natural chemicals for manufacturing pottery, glass, metals, lime plaster, waterproofing. The Mesopotamians had intense interest in medicine and the earliest medical prescriptions appear in Sumerian during the Third Dynasty of Ur. Nonetheless, the Mesopotamians seem to have had little interest in gathering information about the natural world for the mere sake of gathering information and only studied scientific subjects which had obvious practical applications or immediate relevance to their religious system. In the classical world, there is no real ancient analog of a modern scientist. Instead, well-educated upper-class, universally male individuals performed various investigations into nature whenever they could afford the time. Before the invention or discovery of the concept of "nature" by the Pre-Socratic philosophers, the same words tend to be used to describe the natural "way" in which a plant grows, the "way" in which, for example, one tribe worships a particular god.
For this reason, it is claimed these men were the first philosophers in the strict sense, the first people to distinguish "nature" and "convention." Natural philosophy, the precursor of natural science, was thereby distinguished as the knowledge of nature and things which are true for every community, the name of the specialized pursuit of such knowledge was philosophy – the realm of the first philosopher-physicists. They were speculators or theorists interested in astronomy. In contrast, trying to use knowledge of nature to imitate nature was seen by classical scientists as a more appropriate interest for lower class artisans; the early Greek philosophers of the Milesian school, founded by Thales of Miletus and continued by his successors A
An experiment is a procedure carried out to support, refute, or validate a hypothesis. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when a particular factor is manipulated. Experiments vary in goal and scale, but always rely on repeatable procedure and logical analysis of the results. There exists natural experimental studies. A child may carry out basic experiments to understand gravity, while teams of scientists may take years of systematic investigation to advance their understanding of a phenomenon. Experiments and other types of hands-on activities are important to student learning in the science classroom. Experiments can raise test scores and help a student become more engaged and interested in the material they are learning when used over time. Experiments can vary from personal and informal natural comparisons, to controlled. Uses of experiments vary between the natural and human sciences. Experiments include controls, which are designed to minimize the effects of variables other than the single independent variable.
This increases the reliability of the results through a comparison between control measurements and the other measurements. Scientific controls are a part of the scientific method. Ideally, all variables in an experiment are controlled and none are uncontrolled. In such an experiment, if all controls work as expected, it is possible to conclude that the experiment works as intended, that results are due to the effect of the tested variable. In the scientific method, an experiment is an empirical procedure that arbitrates competing models or hypotheses. Researchers use experimentation to test existing theories or new hypotheses to support or disprove them. An experiment tests a hypothesis, an expectation about how a particular process or phenomenon works. However, an experiment may aim to answer a "what-if" question, without a specific expectation about what the experiment reveals, or to confirm prior results. If an experiment is conducted, the results either support or disprove the hypothesis.
According to some philosophies of science, an experiment can never "prove" a hypothesis, it can only add support. On the other hand, an experiment that provides a counterexample can disprove a theory or hypothesis, but a theory can always be salvaged by appropriate ad hoc modifications at the expense of simplicity. An experiment must control the possible confounding factors—any factors that would mar the accuracy or repeatability of the experiment or the ability to interpret the results. Confounding is eliminated through scientific controls and/or, in randomized experiments, through random assignment. In engineering and the physical sciences, experiments are a primary component of the scientific method, they are used to test theories and hypotheses about how physical processes work under particular conditions. Experiments in these fields focus on replication of identical procedures in hopes of producing identical results in each replication. Random assignment is uncommon. In medicine and the social sciences, the prevalence of experimental research varies across disciplines.
When used, experiments follow the form of the clinical trial, where experimental units are randomly assigned to a treatment or control condition where one or more outcomes are assessed. In contrast to norms in the physical sciences, the focus is on the average treatment effect or another test statistic produced by the experiment. A single study does not involve replications of the experiment, but separate studies may be aggregated through systematic review and meta-analysis. There are various differences in experimental practice in each of the branches of science. For example, agricultural research uses randomized experiments, while experimental economics involves experimental tests of theorized human behaviors without relying on random assignment of individuals to treatment and control conditions. One of the first methodical approaches to experiments in the modern sense is visible in the works of the Arab mathematician and scholar Ibn al-Haytham, he conducted his experiments in the field of optics - going back to optical and mathematical problems in the works of Ptolemy - by controlling his experiments due to factors such as self-criticality, reliance on visible results of the experiments as well as a criticality in terms of earlier results.
He counts as one of the first scholars using an inductive-experimental method for achieving results. In his book "Optics" he describes the fundamentally new approach to knowledge and research in an experimental sense: "We should, that is, recommence the inquiry into its principles and premisses, beginning our investigation with an inspection of the things that exist and a survey of the conditions of visible objects. We should distinguish the properties of particulars, gather by induction what pertains to the eye when vision takes place and what is found in the manner of sensation to be uniform, unchanging and not subject to doubt. After which we should ascend in our inquiry and reasonings and orderly, criticizing premisses and exercising caution in regard to conclusions – our aim in all that we make subject to inspect
Metrication or metrification is conversion to the metric system of units of measurement. Worldwide, there has been a long process of independent conversions of countries from various local and traditional systems, beginning in France during the 1790s and spreading over the following two centuries, but the metric system has not been adopted in all countries and sectors. Whilst most countries in the world are using the metric system as their official system of weights and measures, some countries have not committed to adopting it, or have adopted it as their official system but have not completed the process of full metrication. Most countries have adopted the metric system over a transitional period where both units are used for a set period of time; some countries such as Guyana, for example, have adopted the metric system, but have had some trouble over time implementing it. Antigua and Barbuda "officially" metric, is moving toward total implementation of the metric system, but slower than expected.
The government had announced that they have plans to convert their country to the metric system by the first quarter of 2015. Other Caribbean countries such as Saint Lucia are metric but are still in the process toward full conversion. In the United Kingdom the metric system is the official system for most regulated trading by weight or measure purposes, but some imperial units remain the primary official unit of measurement; as of 2018 the UK has only metricated. According to the US Central Intelligence Agency's online The World Factbook, the metric system has not been adopted by Myanmar and the US; the United States use US customary units as does Liberia. Myanmar uses the Burmese units of measurement. According to The Observer, Liberia are committed to adopting the metric system in the future; some sources now identify Liberia as metric, the government of Myanmar has stated that the country would metricate with a goal of completion by 2019. Both Myanmar and Liberia are metric countries, trading internationally in metric units.
Sierra Leone switched to selling fuel by the litre in May 2011. The European Union used the Units of Measure Directive to attempt to achieve a common system of weights and measures and to facilitate the European Single Market. Throughout the 1990s, the European Commission helped accelerate the process for member countries to complete their metric conversion processes. Among them is the United Kingdom where laws in some or all contexts mandate or permit many imperial measures, such as miles and yards for road-sign distances, road speed limits in miles per hour, pints of beer, inches for clothes; the United Kingdom secured permanent exemptions for the mile and yard in road markings, for the pint of draught beer sold in pubs. In 2007, the European Commission announced that it was to abandon the requirement for metric-only labelling on packaged goods, to allow dual metric–imperial marking to continue indefinitely; the United States, the United Kingdom, Canada have some active opposition to metrication where updated weights and measures laws would make obsolete historic systems of measurement.
Other countries, like France and Japan, that once had significant popular opposition to metrication now have complete acceptance of metrication. The Roman empire used the pes measure; this was divided into 12 unciae. The libra was another measure that had wide effect on European weight and currency long after Roman times, e.g. lb, £. The measure came to vary over time. Charlemagne was one of several rulers who launched reform programmes of various kinds to standardise units for measure and currency in his empire, but there was no real general breakthrough. In medieval Europe, local laws on weights and measures were set by trade guilds on a city-by-city basis. For example, the ell or elle was a unit of length used in Europe, but its length varied from 40.2 centimetres in one part of Germany to 70 centimetres in The Netherlands and 94.5 centimetres in Edinburgh. A survey of Switzerland in 1838 revealed that the foot had 37 different regional variations, the ell had 68, there were 83 different measures for dry grain, 70 measures for fluids and 63 different measures for "dead weights".
When Isaac Newton wrote Philosophiae Naturalis Principia Mathematica in 1687, he quoted his measurements in Parisian feet so readers could understand the size. Examples of efforts to have local intercity or national standards for measurements include the Scottish law of 1641, the British standard imperial system of 1824, still used in the United Kingdom. At one time Imperial China had standardised units for volume throughout its territory, but by 1936 official investigations uncovered 53 values for the chi varying from 200 millimetres to 1250 millimetres. However, revolutionary France was to produce the definitive International System of Units which has come to be used by most of the world today; the desire for a single international system of measurement came from growing international trade and the need to apply common standards to goods. For a company to buy a product produced in another country, they need to ensure that the product would arrive as described; the medieval ell was abandoned in part.
One primary advantage of the International Sy
A measuring instrument is a device for measuring a physical quantity. In the physical sciences, quality assurance, engineering, measurement is the activity of obtaining and comparing physical quantities of real-world objects and events. Established standard objects and events are used as units, the process of measurement gives a number relating the item under study and the referenced unit of measurement. Measuring instruments, formal test methods which define the instrument's use, are the means by which these relations of numbers are obtained. All measuring instruments are subject to varying degrees of instrument error and measurement uncertainty. Scientists and other humans use a vast range of instruments to perform their measurements; these instruments may range from simple objects such as rulers and stopwatches to electron microscopes and particle accelerators. Virtual instrumentation is used in the development of modern measuring instruments. In the past, a common time measuring instrument was the sundial.
Today, the usual measuring instruments for time are watches. For accurate measurement of time an atomic clock is used. Stop watches are used to measure time in some sports. Energy is measured by an energy meter. Examples of energy meters include: An electricity meter measures energy directly in kilowatt hours. A gas meter measures energy indirectly by recording the volume of gas used; this figure can be converted to a measure of energy by multiplying it by the calorific value of the gas. A physical system that exchanges energy may be described by the amount of energy exchanged per time-interval called power or flux of energy. For the ranges of power-values see: Orders of magnitude. Action describes, its dimension is the same as that of an angular momentum. A phototube provides a voltage measurement which permits the calculation of the quantized action of light. See photoelectric effect; this includes basic quantities found in classical- and continuum mechanics. Length, distance, or range meterFor the ranges of length-values see: Orders of magnitude PlanimeterFor the ranges of area-values see: Orders of magnitude Buoyant weight Overflow trough Measuring cup Flow measurement devices Graduated cylinder Pipette Eudiometer, pneumatic trough If the mass density of a solid is known, weighing allows to calculate the volume.
For the ranges of volume-values see: Orders of magnitude Gas meter Mass flow meter Metering pump Water meter Airspeed indicator Radar gun, a Doppler radar device, using the Doppler effect for indirect measurement of velocity. LIDAR speed gun Speedometer Tachometer Tachymeter VariometerFor the ranges of speed-values see: Orders of magnitude Accelerometer Balance Automatic checkweighing machines Katharometer Weighing scales Inertial balance Mass spectrometers measure the mass-to-charge ratio, not the mass. For the ranges of mass-values see: Orders of magnitude Ballistic pendulum Force gauge Spring scale Strain gauge Torsion balance Tribometer Anemometer Barometer used to measure the atmospheric pressure. Manometer see pressure measurement and pressure sensor Pitot tube Tire-pressure gauge in industry and mobilityFor the ranges of pressure-values see: Orders of magnitude Circumferentor Cross staff Goniometer Graphometer Protractor Quadrant Reflecting instruments Octant Reflecting circles Sextant Theodolite Stroboscope TachometerFor the value-ranges of angular velocity see: Orders of magnitude For the ranges of frequency see: Orders of magnitude Dynamometer de Prony brake Torque wrench See the section about navigation below.
Dumpy level Laser line level Spirit level Gyroscope Ballistic pendulum, indirectly by calculation and or gauging Considerations related to electric charge dominate electricity and electronics. Electrical charges interact via a field; that field is called electric field. If the charge doesn't move. If the charge moves, thus realizing an electric current in an electrically neutral conductor, that field is called magnetic. Electricity can be given a quality — a potential, and electricity has the electric charge. Energy in elementary electrodynamics is calculated by multiplying the potential by the amount of charge found at that potential: potential times charge. Electrometer is used to reconfirm the phenomenon of contact electricity leading to triboelectric sequences. Torsion balance force, see above. For the ranges of charge values see: Orders of magnitude Ammeter Clamp meter Galvanometer D'Arsonval galvanometer Oscilloscope allows quantifying time-dependent voltages Voltmeter Ohmmeter Time-domain reflectometer characterizes and locates faults in metallic cables by runtime measurements of electric signals.
Wheatstone bridge Capacitance meter Inductance meter Electric energy meter Electricity meter Wattmeter Field mill See the relevant section in the article about the magnetic field. Compass Hall effect sensor Magnetometer Proton magnetometer SQUIDFor the ranges of magnetic field see: Orders of magnitude Multimeter, combines the functions of ammeter and ohmmeter as a minimum. LCR meter, combines the functions of ohmmeter, capacitance meter and inductance meter
Image resolution is the detail an image holds. The term applies to raster digital images, film images, other types of images. Higher resolution means more image detail. Image resolution can be measured in various ways. Resolution quantifies. Resolution units can be tied to physical sizes, to the overall size of a picture, or to angular subtense. Line pairs are used instead of lines. A line is either a light line. A resolution of 10 lines per millimeter means 5 dark lines alternating with 5 light lines, or 5 line pairs per millimeter. Photographic lens and film resolution are most quoted in line pairs per millimeter; the resolution of digital cameras can be described in many different ways. The term resolution is considered equivalent to pixel count in digital imaging, though international standards in the digital camera field specify it should instead be called "Number of Total Pixels" in relation to image sensors, as "Number of Recorded Pixels" for what is captured. Hence, CIPA DCG-001 calls for notation such as "Number of Recorded Pixels 1000 × 1500".
According to the same standards, the "Number of Effective Pixels" that an image sensor or digital camera has is the count of pixel sensors that contribute to the final image, as opposed to the number of total pixels, which includes unused or light-shielded pixels around the edges. An image of N pixels height by M pixels wide can have any resolution less than N lines per picture height, or N TV lines, but when the pixel counts are referred to as "resolution", the convention is to describe the pixel resolution with the set of two positive integer numbers, where the first number is the number of pixel columns and the second is the number of pixel rows, for example as 7680 × 6876. Another popular convention is to cite resolution as the total number of pixels in the image given as number of megapixels, which can be calculated by multiplying pixel columns by pixel rows and dividing by one million. Other conventions include describing pixels per length unit or pixels per area unit, such as pixels per inch or per square inch.
None of these pixel resolutions are true resolutions, but they are referred to as such. Below is an illustration of how the same image might appear at different pixel resolutions, if the pixels were poorly rendered as sharp squares. An image, 2048 pixels in width and 1536 pixels in height has a total of 2048×1536 = 3,145,728 pixels or 3.1 megapixels. One could refer to it as 2048 by a 3.1-megapixel image. Or, you can think of it as a low quality image if printed at about 28.5 inches wide, or a good quality image if printed at about 7 inches wide. The count of pixels isn't a real measure of the resolution of digital camera images, because color image sensors are set up to alternate color filter types over the light sensitive individual pixel sensors. Digital images require a red and blue value for each pixel to be displayed or printed, but one individual pixel in the image sensor will only supply one of those three pieces of information; the image has to be demosaiced to produce all three colors for each output pixel.
The terms blurriness and sharpness are used for digital images but other descriptors are used to reference the hardware capturing and displaying the images. Spatial resolution in radiology refers to the ability of the imaging modality to differentiate two objects. Low spatial resolution techniques will be unable to differentiate between two objects that are close together; the measure of how lines can be resolved in an image is called spatial resolution, it depends on properties of the system creating the image, not just the pixel resolution in pixels per inch. For practical purposes the clarity of the image is decided by its spatial resolution, not the number of pixels in an image. In effect, spatial resolution refers to the number of independent pixel values per unit length; the spatial resolution of consumer displays range from 50 to 800 pixel lines per inch. With scanners, optical resolution is sometimes used to distinguish spatial resolution from the number of pixels per inch. In remote sensing, spatial resolution is limited by diffraction, as well as by aberrations, imperfect focus, atmospheric distortion.
The ground sample distance of an image, the pixel spacing on the Earth's surface, is considerably smaller than the resolvable spot size. In astronomy, one measures spatial resolution in data points per arcsecond subtended at the point of observation, because the physical distance between objects in the image depends on their distance away and this varies with the object of interest. On the other hand, in electron microscopy, line or fringe resolution refers to the minimum separation detectable between adjacent parallel lines, whereas point resolution instead refers to the minimum separation between adjacent points that can be both detected and interpreted e.g. as adjacent columns of atoms, for instance. The former helps one detect periodicity in specimens, whereas the latter is key to visualizing how individual atoms interact. In Stereoscopic 3D
A contract is a legally-binding agreement which recognises and governs the rights and duties of the parties to the agreement. A contract is enforceable because it meets the requirements and approval of the law. An agreement involves the exchange of goods, money, or promises of any of those. In the event of breach of contract, the law awards the injured party access to legal remedies such as damages and cancellation. In the Anglo-American common law, formation of a contract requires an offer, consideration, a mutual intent to be bound; each party must have capacity to enter the contract. Although most oral contracts are binding, some types of contracts may require formalities such as being in writing or by deed. In the civil law tradition, contract law is a branch of the law of obligations. At common law, the elements of a contract are offer, intention to create legal relations and legality of both form and content. Not all agreements are contractual, as the parties must be deemed to have an intention to be bound.
A so-called gentlemen's agreement is one, not intended to be enforceable, "binding in honour only". In order for a contract to be formed, the parties must reach mutual assent; this is reached through offer and an acceptance which does not vary the offer's terms, known as the "mirror image rule". An offer is a definite statement of the offeror's willingness to be bound should certain conditions be met. If a purported acceptance does vary the terms of an offer, it is not an acceptance but a counteroffer and, therefore a rejection of the original offer; the Uniform Commercial Code disposes of the mirror image rule in §2-207, although the UCC only governs transactions in goods in the USA. As a court cannot read minds, the intent of the parties is interpreted objectively from the perspective of a reasonable person, as determined in the early English case of Smith v Hughes, it is important to note that where an offer specifies a particular mode of acceptance, only an acceptance communicated via that method will be valid.
Contracts may be unilateral. A bilateral contract is an agreement in which each of the parties to the contract makes a promise or set of promises to each other. For example, in a contract for the sale of a home, the buyer promises to pay the seller $200,000 in exchange for the seller's promise to deliver title to the property; these common contracts take place in the daily flow of commerce transactions, in cases with sophisticated or expensive precedent requirements, which are requirements that must be met for the contract to be fulfilled. Less common are unilateral contracts in which one party makes a promise, but the other side does not promise anything. In these cases, those accepting the offer are not required to communicate their acceptance to the offeror. In a reward contract, for example, a person who has lost a dog could promise a reward if the dog is found, through publication or orally; the payment could be additionally conditioned on the dog being returned alive. Those who learn of the reward are not required to search for the dog, but if someone finds the dog and delivers it, the promisor is required to pay.
In the similar case of advertisements of deals or bargains, a general rule is that these are not contractual offers but an "invitation to treat", but the applicability of this rule is disputed and contains various exceptions. The High Court of Australia stated that the term unilateral contract is "unscientific and misleading". In certain circumstances, an implied contract may be created. A contract is implied in fact if the circumstances imply that parties have reached an agreement though they have not done so expressly. For example, John Smith, a former lawyer may implicitly enter a contract by visiting a doctor and being examined. A contract, implied in law is called a quasi-contract, because it is not in fact a contract. Quantum meruit claims are an example. Where something is advertised in a newspaper or on a poster, the advertisement will not constitute an offer but will instead be an invitation to treat, an indication that one or both parties are prepared to negotiate a deal. An exception arises if the advertisement makes a unilateral promise, such as the offer of a reward, as in the famous case of Carlill v Carbolic Smoke Ball Co, decided in nineteenth-century England.
The company, a pharmaceutical manufacturer, advertised a smoke ball that would, if sniffed "three times daily for two weeks", prevent users from catching the'flu. If the smoke ball failed to prevent'flu, the company promised that they would pay the user £100, adding that they had "deposited £1,000 in the Alliance Bank to show our sincerity in the matter"; when Mrs Carlill sued for the money, the company argued the advert should not be taken as a serious binding offer. Although an invitation to treat cannot be accepted, it should not be ignored, for it may affect the offer. For instance, where an offer is made in response to an invitation to treat, the offer may incorporate the terms of the invitation to treat. If, as in the Boots case, the offer is made by an action without any