The ecliptic is the mean plane of the apparent path in the Earth's sky that the Sun follows over the course of one year. This plane of reference is coplanar with Earth's orbit around the Sun; the ecliptic is not noticeable from Earth's surface because the planet's rotation carries the observer through the daily cycles of sunrise and sunset, which obscure the Sun's apparent motion against the background of stars during the year. The motions as described above are simplifications. Due to the movement of Earth around the Earth–Moon center of mass, the apparent path of the Sun wobbles with a period of about one month. Due to further perturbations by the other planets of the Solar System, the Earth–Moon barycenter wobbles around a mean position in a complex fashion; the ecliptic is the apparent path of the Sun throughout the course of a year. Because Earth takes one year to orbit the Sun, the apparent position of the Sun takes one year to make a complete circuit of the ecliptic. With more than 365 days in one year, the Sun moves a little less than 1° eastward every day.
This small difference in the Sun's position against the stars causes any particular spot on Earth's surface to catch up with the Sun about four minutes each day than it would if Earth would not orbit. Again, this is a simplification, based on a hypothetical Earth that orbits at uniform speed around the Sun; the actual speed with which Earth orbits the Sun varies during the year, so the speed with which the Sun seems to move along the ecliptic varies. For example, the Sun is north of the celestial equator for about 185 days of each year, south of it for about 180 days; the variation of orbital speed accounts for part of the equation of time. Because Earth's rotational axis is not perpendicular to its orbital plane, Earth's equatorial plane is not coplanar with the ecliptic plane, but is inclined to it by an angle of about 23.4°, known as the obliquity of the ecliptic. If the equator is projected outward to the celestial sphere, forming the celestial equator, it crosses the ecliptic at two points known as the equinoxes.
The Sun, in its apparent motion along the ecliptic, crosses the celestial equator at these points, one from south to north, the other from north to south. The crossing from south to north is known as the vernal equinox known as the first point of Aries and the ascending node of the ecliptic on the celestial equator; the crossing from north to south is descending node. The orientation of Earth's axis and equator are not fixed in space, but rotate about the poles of the ecliptic with a period of about 26,000 years, a process known as lunisolar precession, as it is due to the gravitational effect of the Moon and Sun on Earth's equatorial bulge; the ecliptic itself is not fixed. The gravitational perturbations of the other bodies of the Solar System cause a much smaller motion of the plane of Earth's orbit, hence of the ecliptic, known as planetary precession; the combined action of these two motions is called general precession, changes the position of the equinoxes by about 50 arc seconds per year.
Once again, this is a simplification. Periodic motions of the Moon and apparent periodic motions of the Sun cause short-term small-amplitude periodic oscillations of Earth's axis, hence the celestial equator, known as nutation; this adds a periodic component to the position of the equinoxes. Obliquity of the ecliptic is the term used by astronomers for the inclination of Earth's equator with respect to the ecliptic, or of Earth's rotation axis to a perpendicular to the ecliptic, it is about 23.4° and is decreasing 0.013 degrees per hundred years due to planetary perturbations. The angular value of the obliquity is found by observation of the motions of Earth and other planets over many years. Astronomers produce new fundamental ephemerides as the accuracy of observation improves and as the understanding of the dynamics increases, from these ephemerides various astronomical values, including the obliquity, are derived; until 1983 the obliquity for any date was calculated from work of Newcomb, who analyzed positions of the planets until about 1895: ε = 23° 27′ 08″.26 − 46″.845 T − 0″.0059 T2 + 0″.00181 T3 where ε is the obliquity and T is tropical centuries from B1900.0 to the date in question.
From 1984, the Jet Propulsion Laboratory's DE series of computer-generated ephemerides took over as the fundamental ephemeris of the Astronomical Almanac. Obliquity based on DE200, which analyzed observations from 1911 to 1979, was calculated: ε = 23° 26′ 21″.45 − 46″.815 T − 0″.0006 T2 + 0″.00181 T3 where hereafter T is Julian centuries from J2000.0. JPL's fundamental ephemerides have been continually updated; the Astronomical Almanac for 2010 specifies:ε = 23° 26′ 21″.406 − 46″.836769 T − 0″.0001831 T2 + 0″.00200340 T3 − 0″.576×10−6 T4 − 4″.34×10−8 T5 These expressions for the obliquity are intended for high precision over a short time span ± several centuries. J. Laskar computed an expression to order T10 good to 0″.04/1000 years over 10,000 years. All of these expressions are for the mean obliquity, that is, without the nutation of the equator included; the true or instantaneous obliquity includes the nutation. Most of the major bodies of the Solar System o
A constellation is a group of stars that forms an imaginary outline or pattern on the celestial sphere representing an animal, mythological person or creature, a god, or an inanimate object. The origins of the earliest constellations go back to prehistory. People used them to relate stories of their beliefs, creation, or mythology. Different cultures and countries adopted their own constellations, some of which lasted into the early 20th century before today's constellations were internationally recognized. Adoption of constellations has changed over time. Many have changed in shape; some became popular. Others were limited to single nations; the 48 traditional Western constellations are Greek. They are given in Aratus' work Phenomena and Ptolemy's Almagest, though their origin predates these works by several centuries. Constellations in the far southern sky were added from the 15th century until the mid-18th century when European explorers began traveling to the Southern Hemisphere. Twelve ancient constellations belong to the zodiac.
The origins of the zodiac remain uncertain. In 1928, the International Astronomical Union formally accepted 88 modern constellations, with contiguous boundaries that together cover the entire celestial sphere. Any given point in a celestial coordinate system lies in one of the modern constellations; some astronomical naming systems include the constellation where a given celestial object is found to convey its approximate location in the sky. The Flamsteed designation of a star, for example, consists of a number and the genitive form of the constellation name. Other star patterns or groups called asterisms are not constellations per se but are used by observers to navigate the night sky. Examples of bright asterisms include the Pleiades and Hyades within the constellation Taurus or Venus' Mirror in the constellation of Orion.. Some asterisms, like the False Cross, are split between two constellations; the word "constellation" comes from the Late Latin term cōnstellātiō, which can be translated as "set of stars".
The Ancient Greek word for constellation is ἄστρον. A more modern astronomical sense of the term "constellation" is as a recognisable pattern of stars whose appearance is associated with mythological characters or creatures, or earthbound animals, or objects, it can specifically denote the recognized 88 named constellations used today. Colloquial usage does not draw a sharp distinction between "constellations" and smaller "asterisms", yet the modern accepted astronomical constellations employ such a distinction. E.g. the Pleiades and the Hyades are both asterisms, each lies within the boundaries of the constellation of Taurus. Another example is the northern asterism known as the Big Dipper or the Plough, composed of the seven brightest stars within the area of the IAU-defined constellation of Ursa Major; the southern False Cross asterism includes portions of the constellations Carina and Vela and the Summer Triangle.. A constellation, viewed from a particular latitude on Earth, that never sets below the horizon is termed circumpolar.
From the North Pole or South Pole, all constellations south or north of the celestial equator are circumpolar. Depending on the definition, equatorial constellations may include those that lie between declinations 45° north and 45° south, or those that pass through the declination range of the ecliptic or zodiac ranging between 23½° north, the celestial equator, 23½° south. Although stars in constellations appear near each other in the sky, they lie at a variety of distances away from the Earth. Since stars have their own independent motions, all constellations will change over time. After tens to hundreds of thousands of years, familiar outlines will become unrecognizable. Astronomers can predict the past or future constellation outlines by measuring individual stars' common proper motions or cpm by accurate astrometry and their radial velocities by astronomical spectroscopy; the earliest evidence for the humankind's identification of constellations comes from Mesopotamian inscribed stones and clay writing tablets that date back to 3000 BC.
It seems that the bulk of the Mesopotamian constellations were created within a short interval from around 1300 to 1000 BC. Mesopotamian constellations appeared in many of the classical Greek constellations; the oldest Babylonian star catalogues of stars and constellations date back to the beginning in the Middle Bronze Age, most notably the Three Stars Each texts and the MUL. APIN, an expanded and revised version based on more accurate observation from around 1000 BC. However, the numerous Sumerian names in these catalogues suggest that they built on older, but otherwise unattested, Sumerian traditions of the Early Bronze Age; the classical Zodiac is a revision of Neo-Babylonian constellations from the 6th century BC. The Greeks adopted the Babylonian constellations in the 4th century BC. Twenty Ptolemaic constellations are from the Ancient Near East. Another ten have the same stars but different names. Biblical scholar, E. W. Bullinger interpreted some of the creatures mentioned in the books of Ezekiel and Revelation as the middle signs of the four quarters of the Zodiac, with the Lion as Leo, the Bull as Taurus, the Man representing Aquarius and the Eagle standing in for Scorpio.
The biblical Book of Job also
The Nisga’a formerly spelled Nishga and spelled in the Nisga’a language as Nisg̱a’a, are an Indigenous people of Canada in British Columbia. They reside in the Nass River valley of northwestern British Columbia; the name is a reduced form of, a loan word from Tongass Tlingit, where it means "people of the Nass River". The official languages of Nisg̱a' a are English. Nisga’a society is organized into four tribes: G̱anada Gisḵ’aast Lax̱gibuu Lax̱sgiik Each tribe is further sub-divided into house groups – extended families with same origins; some houses are grouped together into clans – grouping of Houses with same ancestors. Example: Lax̱gibuu Tribe Gitwilnaak’il Clan House of Duuḵ House of K’eex̱kw House of Gwingyoo The Nisga’a traditionally harvest "beach food" all year round; this might include razor clams, oysters, scallops, fish and other seafood that can be harvested from the shore. They harvest salmon, char, pike and other fresh water fish from the streams, hunt seals and sea lion. Oolichan grease is sometimes traded with other tribes, though nowadays this is more in a ceremonial context.
They hunt mountain goat, game birds and more in the forests. The family works together to process the meat and fish, roasting or boiling the former, they eat fish and sea mammals in frozen, dried or roasted form. The heads of a type of cod gathered half eaten by sharks, are boiled into a soup that helped prevent colds; the Nisga′a trade dried fish, seal oil, fish oil and cedar. The traditional houses of the Nisga’a are shaped as large rectangles, made of cedar planks with cedar shake roofs, oriented with the doors facing the water; the doors are decorated with the family crest. Inside, the floor is dug down to conserve temperature. Beds and boxes of possessions are placed around the walls. Prior to the mid twentieth century, around three to four extended families might live in one house: this is nowadays an uncommon practice. Masks and blankets might decorate the walls. Prior to European colonisation, men wore nothing in the summer the best time to hunt and fish. Women wore skirts went topless. During the colder season, men wore cedar bark skirts, a cape of cedar bark, a basket hat outside in the rain, but wore nothing inside the house.
Women outdoors. Both sexes wore shell and bone necklaces, they rubbed seal blubber into their hair, men kept their hair long or in a top knot. During warfare, men wore red cedar armour, a cedar helmet, cedar loincloths, they wielded spears, harpoons and slings. Wicker shields were common. 2,000 live in the Nass Valley. Another 5,000 Nisga’a live elsewhere in Canada, predominantly within the three urban societies noted in the section below; the Nisga’a people number about 7,000. In British Columbia, the Nisga’a Nation is represented by four villages: Gitlax̱t'aamiks - nearly 800 Gitwinksihlkw - 200 Lax̱g̱alts’ap - more than 500 Ging̱olx - 400 Many Nisga’a people have moved to cities for their opportunities. Concentrations are found in three urban areas outside traditional Nisga’a territory: Terrace, British Columbia Prince Rupert/Port Edward Vancouver - there are 1,500 Nisga'a in Vancouver, others elsewhere in the Lower Mainland; the Nisga'a calendar revolves around harvesting of goods used. The original year followed the various moons throughout the year.
Hobiyee: Like a Spoon. This is the traditional time to celebrate the new year known as Hoobiyee. X̱saak: To Eat Oolichans; the oolichans return to the Nass River the end of February/beginning of March. The oolichans are the first food harvested after the winter, which marks the beginning of the harvesting year. Mmaal: To Use Canoes Again; the ice begins to break on the river, allowing for canoes to be used again Yansa’alt: Leaves Are Blooming. The leaves begin to flourish once again Miso’o: Sockeye Salmon. Sockeye salmon are harvested X̱maay: To Eat Berries. Various berries are harvested Wii Hoon: Great Salmon. Great amounts of salmon are harvested Genuugwiikw: Trail of the Marmot. Small game such as marmots are hunted X̱laaxw: To Eat Trout. Trout are the main staple for this month Gwilatkw: To Blanket; the earth is "Blanketed" with snow Luut’aa: To Sit. The sun is sitting in one spot Ḵ’aliiyee: To Walk North; this time of year, the sun begins to go north again Buxwlaks: To Blow Around. Blow around refers to the amount of wind during this time of year On August 4, 1998, a land-claim was settled between the Nisga’a, the government of British Columbia, the Government of Canada.
As part of the settlement in the Nass River valley, nearly 2,000 square kilometres of land was recognized as Nisga’a, a 300,000-cubic-decameter water reservation was created. The Bear Glacier Provincial Park was created as a result of this agreement; the land-claim's settlement was the first formal treaty signed by a First Nation in British Columbia since the Douglas Treaties in 1854 and Treaty 8. The land, owned collectively is exposed to internal pressures from the Nisga'a people to turn it over i
A season is a division of the year marked by changes in weather and amount of daylight. On Earth, seasons result from Earth's orbit around the Sun and Earth's axial tilt relative to the ecliptic plane. In temperate and polar regions, the seasons are marked by changes in the intensity of sunlight that reaches the Earth's surface, variations of which may cause animals to undergo hibernation or to migrate, plants to be dormant. Various cultures define the nature of seasons based on regional variations. During May and July, the Northern Hemisphere is exposed to more direct sunlight because the hemisphere faces the Sun; the same is true of the Southern Hemisphere in November and January. It is Earth's axial tilt that causes the Sun to be higher in the sky during the summer months, which increases the solar flux. However, due to seasonal lag, June and August are the warmest months in the Northern Hemisphere while December and February are the warmest months in the Southern Hemisphere. In temperate and subpolar regions, four seasons based on the Gregorian calendar are recognized: spring, autumn or fall, winter.
The definition of seasons is cultural. In India from the ancient times, six seasons or Ritu based on south Asian religious or cultural calendars are recognised and identified today for the purposes such as agriculture and trade. Ecologists use a six-season model for temperate climate regions which are not tied to any fixed calendar dates: prevernal, estival, serotinal and hibernal. Many tropical regions have monsoon season and the dry season; some have a third mild, or harmattan season. Seasons held special significance for agrarian societies, whose lives revolved around planting and harvest times, the change of seasons was attended by ritual. In some parts of the world, some other "seasons" capture the timing of important ecological events such as hurricane season, tornado season, wildfire season; the most important of these are the three seasons—flood and low water—which were defined by the former annual flooding of the Nile in Egypt. The seasons result from the Earth's axis of rotation being tilted with respect to its orbital plane by an angle of 23.4 degrees.
Regardless of the time of year, the northern and southern hemispheres always experience opposite seasons. This is because during summer or winter, one part of the planet is more directly exposed to the rays of the Sun than the other, this exposure alternates as the Earth revolves in its orbit. For half of the year, the Northern Hemisphere tips toward the Sun, with the maximum amount occurring on about June 21. For the other half of the year, the same happens, but in the Southern Hemisphere instead of the Northern, with the maximum around December 21; the two instants when the Sun is directly overhead at the Equator are the equinoxes. At that moment, both the North Pole and the South Pole of the Earth are just on the terminator, hence day and night are divided between the two hemispheres. Around the March equinox, the Northern Hemisphere will be experiencing spring as the hours of daylight increase, the Southern Hemisphere is experiencing autumn as daylight hours shorten; the effect of axial tilt is observable as the change in day length and altitude of the Sun at solar noon during the year.
The low angle of Sun during the winter months means that incoming rays of solar radiation are spread over a larger area of the Earth's surface, so the light received is more indirect and of lower intensity. Between this effect and the shorter daylight hours, the axial tilt of the Earth accounts for most of the seasonal variation in climate in both hemispheres. Compared to axial tilt, other factors contribute little to seasonal temperature changes; the seasons are not the result of the variation in Earth's distance to the Sun because of its elliptical orbit. In fact, Earth reaches perihelion in January, it reaches aphelion in July, so the slight contribution of orbital eccentricity opposes the temperature trends of the seasons in the Northern Hemisphere. In general, the effect of orbital eccentricity on Earth's seasons is a 7% variation in sunlight received. Orbital eccentricity can influence temperatures, but on Earth, this effect is small and is more than counteracted by other factors; this is because the Northern Hemisphere has more land than the Southern, land warms more than sea.
Any noticeable intensification of southern winters and summers due to Earth's elliptical orbit is mitigated by the abundance of water in the Southern Hemisphere. Seasonal weather fluctuations depend on factors such as proximity to oceans or other large bodies of water, currents in those oceans, El Niño/ENSO and other oceanic cycles, prevailing winds. In the temperate and polar regions, seasons are marked by changes in the amount of sunlight, which in turn causes cycles of dormancy in plants and hibernation in animals; these effects vary with proximity to bodies of water. For example, the South Pole is in the middle of the continent of Antarctica and therefore a considerable distance from the moderating influence of the southern oceans; the North Pole is in the Arctic Ocean, thus its temperature extremes are buffered by the water. The result is that the South Pole is colder during the southern winter than the North Pole dur
The full moon is the lunar phase when the Moon appears illuminated from Earth's perspective. This occurs when Earth is located between the Moon; this means that the lunar hemisphere facing Earth – the near side – is sunlit and appears as a circular disk, while the far side is dark. The full moon occurs once every month; when the Moon moves into Earth's shadow, a lunar eclipse occurs, during which all or part of the Moon's face may appear reddish due to the Rayleigh scattering of blue wavelengths and the refraction of sunlight through Earth's atmosphere. Lunar eclipses happen only during full moon and around points on its orbit where the satellite may pass through the planet's shadow. A lunar eclipse does not occur every month because the Moon's orbit is inclined 5.14° with respect to the ecliptic plane of Earth. Lunar eclipses happen only. Therefore, a lunar eclipse occurs every 6 months and 2 weeks before or after a solar eclipse, which occurs during new moon around the opposite node; the interval period between a new or full moon and the next same phase, a synodic month, averages about 29.53 days.
Therefore, in those lunar calendars in which each month begins on the day of the new moon, the full moon falls on either the 14th or 15th day of the lunar month. Because a calendar month consists of a whole number of days, a lunar month may be either 29 or 30 days long. A full moon is thought of as an event of a full night's duration; this is somewhat misleading because its phase seen from Earth continuously wanes. Its maximum illumination occurs at the moment waxing. For any given location, about half of these maximum full moons may be visible, while the other half occurs during the day, when the full moon is below the horizon. Many almanacs list full moons not only by date, but by their exact time in Coordinated Universal Time. Typical monthly calendars that include lunar phases may be offset by one day when used in a different time zone. Full moon is a suboptimal time for astronomical observation of the Moon because shadows vanish, it is a poor time for other observations because the bright sunlight reflected by the Moon, amplified by the opposition surge outshines many stars.
On 12 December 2008, the full moon occurred closer to the Earth than it had been at any time for the previous 15 years, called a supermoon. On 19 March 2011, another full supermoon occurred, closer to the Earth than at any time for the previous 18 years. On 14 November 2016, a full supermoon occurred closer to the Earth than at any time for the previous 68 years; the date and approximate time of a specific full moon can be calculated from the following equation: d = 20.362000 + 29.530588861 × N + 102.026 × 10 − 12 × N 2 where d is the number of days since 1 January 2000 00:00:00 in the Terrestrial Time scale used in astronomical ephemerides. The true time of a full moon may differ from this approximation by up to about 14.5 hours as a result of the non-circularity of the moon's orbit. See New moon for an explanation of the formula and its parameters; the age and apparent size of the full moon vary in a cycle of just under 14 synodic months, referred to as a full moon cycle. Full moons are traditionally associated with temporal insomnia and various "magical phenomena" such as lycanthropy.
Psychologists, have found that there is no strong evidence for effects on human behavior around the time of a full moon. They find that studies are not consistent, with some showing a positive effect and others showing a negative effect. In one instance, the 23 December 2000 issue of the British Medical Journal published two studies on dog bite admission to hospitals in England and Australia; the study of the Bradford Royal Infirmary found that dog bites were twice as common during a full moon, whereas the study conducted by the public hospitals in Australia found that they were less likely. Month names are names of moons in lunisolar calendars. Since the introduction of the solar Julian calendar in the Roman Empire, the Gregorian calendar worldwide, people no longer perceive month names as "moon" names; the traditional Old English month names were equated with the names of the Julian calendar from an early time. Some full moons have developed new names in modern times, e.g. the blue moon, the names "harvest moon" and "hunter's moon" for the full moons of autumn.
Lunar eclipses only happen during a full moon and cast a reddish tint over the face of the moon. This has been called a blood moon in popular culture; the "harvest moon" and "hunter's moon" are traditional terms for the full moons occurri
Culture is the social behavior and norms found in human societies. Culture is considered a central concept in anthropology, encompassing the range of phenomena that are transmitted through social learning in human societies. Cultural universals are found in all human societies; the concept of material culture covers the physical expressions of culture, such as technology and art, whereas the immaterial aspects of culture such as principles of social organization, philosophy and science comprise the intangible cultural heritage of a society. In the humanities, one sense of culture as an attribute of the individual has been the degree to which they have cultivated a particular level of sophistication in the arts, education, or manners; the level of cultural sophistication has sometimes been seen to distinguish civilizations from less complex societies. Such hierarchical perspectives on culture are found in class-based distinctions between a high culture of the social elite and a low culture, popular culture, or folk culture of the lower classes, distinguished by the stratified access to cultural capital.
In common parlance, culture is used to refer to the symbolic markers used by ethnic groups to distinguish themselves visibly from each other such as body modification, clothing or jewelry. Mass culture refers to the mass-produced and mass mediated forms of consumer culture that emerged in the 20th century; some schools of philosophy, such as Marxism and critical theory, have argued that culture is used politically as a tool of the elites to manipulate the lower classes and create a false consciousness, such perspectives are common in the discipline of cultural studies. In the wider social sciences, the theoretical perspective of cultural materialism holds that human symbolic culture arises from the material conditions of human life, as humans create the conditions for physical survival, that the basis of culture is found in evolved biological dispositions; when used as a count noun, a "culture" is the set of customs and values of a society or community, such as an ethnic group or nation. Culture is the set of knowledge acquired over time.
In this sense, multiculturalism values the peaceful coexistence and mutual respect between different cultures inhabiting the same planet. Sometimes "culture" is used to describe specific practices within a subgroup of a society, a subculture, or a counterculture. Within cultural anthropology, the ideology and analytical stance of cultural relativism holds that cultures cannot be objectively ranked or evaluated because any evaluation is situated within the value system of a given culture; the modern term "culture" is based on a term used by the Ancient Roman orator Cicero in his Tusculanae Disputationes, where he wrote of a cultivation of the soul or "cultura animi," using an agricultural metaphor for the development of a philosophical soul, understood teleologically as the highest possible ideal for human development. Samuel Pufendorf took over this metaphor in a modern context, meaning something similar, but no longer assuming that philosophy was man's natural perfection, his use, that of many writers after him, "refers to all the ways in which human beings overcome their original barbarism, through artifice, become human."In 1986, philosopher Edward S.
Casey wrote, "The word culture meant'place tilled' in Middle English, the same word goes back to Latin colere,'to inhabit, care for, worship' and cultus,'A cult a religious one.' To be cultural, to have a culture, is to inhabit a place sufficiently intensive to cultivate it—to be responsible for it, to respond to it, to attend to it caringly." Culture described by Richard Velkley:... meant the cultivation of the soul or mind, acquires most of its modern meaning in the writings of the 18th-century German thinkers, who were on various levels developing Rousseau's criticism of "modern liberalism and Enlightenment". Thus a contrast between "culture" and "civilization" is implied in these authors when not expressed as such. In the words of anthropologist E. B. Tylor, it is "that complex whole which includes knowledge, art, law and any other capabilities and habits acquired by man as a member of society." Alternatively, in a contemporary variant, "Culture is defined as a social domain that emphasizes the practices and material expressions, over time, express the continuities and discontinuities of social meaning of a life held in common.
The Cambridge English Dictionary states that culture is "the way of life the general customs and beliefs, of a particular group of people at a particular time." Terror management theory posits that culture is a series of activities and worldviews that provide humans with the basis for perceiving themselves as "person of worth within the world of meaning"—raising themselves above the physical aspects of existence, in order to deny the animal insignificance and death that Homo sapiens became aware of when they acquired a larger brain. The word is used in a general sense as the evolved ability to categorize and represent experiences with symbols and to act imaginatively and creatively; this ability arose with the evolution of behavioral modernity in humans around 50,000 years ago, is thought to be unique to humans, although some other species have demonstrated similar, though much less complex, abilities for social learning. It is used to denote the co