Annum is a Latin noun meaning year. It is the accusative singular of the second declension masculine noun annus (nominative), anni (genitive) [1]. Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... The term accusative may be used in the following contexts: A form of morphosyntactic alignment, as found in nominative-accusative languages. ... In linguistics, grammatical number is a morphological category characterized by the expression of quantity through inflection or agreement. ... In linguistics, declension is the inflection of nouns, pronouns and adjectives to indicate such features as number (typically singular vs. ... The word masculine can refer to: the property of being biologically male masculinity, a traditionally male gender role the masculine grammatical gender This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Noun or noun substantive is a lexical category which is defined in terms of how its members combine with other grammatical kinds of expressions. ...

As a unit of time, it is defined as exactly 365.25 days (that is, the average length of a year in the Julian calendar) of 86,400 seconds, representing the duration of one revolution of the Earth around the Sun. Although there is no universally accepted symbol for the year, NIST^[1] and ISO 31-1^[2] suggest the symbol a (in the International System of Units a is also the symbol for the are unit of area, but context is usually enough to disambiguate). In English, the abbreviation yr is frequently used as well. The Julian calendar was introduced in 46 BC by Julius Caesar and came into force in 45 BC (709 ab urbe condita). ... Cover of brochure The International System of Units. ... An are (symbol a) is a unit of area, equal to 100 square meters (10 m × 10 m), used for measuring land area. ...

• Per annum means "yearly".

• Kilo-annum, usual symbol ka, is a unit of time equal to one thousand years.

• Mega-annum, usual symbol Ma, is a unit of time equal to one million (10⁶) years. It is commonly used in scientific disciplines such as geology, paleontology, and celestial mechanics to signify very long time periods in the past. For example, the dinosaur species Tyrannosaurus rex was abundant approximately 65 Ma (65 million years) ago (ago may not always be mentioned; if the quantity is specified while not explicitly discussing a duration, one can assume that "ago" is implied; "mya" includes "ago" explicitly.). In astronomical applications, the year used is the Julian year of precisely 365.25 days.

• Giga-annum, usual symbol Ga, is a unit of time equal to one billion (10⁹) years. It is commonly used in scientific disciplines such as cosmology and geology to signify extremely long time periods in the past. For example, the formation of the Earth occurred approximately 4.57 Ga (4.57 billion years) ago. As is clear from the notation, billion as used here is on the short scale, also known as the American English preference.

• Exa-annum, usual symbol Ea, is a unit of time equal to (10¹⁸) years (one quintillion on the short scale, one trillion on the long scale). It is an extremely long unit of time. The half-life of tungsten-180 is 1.8 Ea.

A millennium (pl. ... For the techno single by Moby, see Thousand (single). ... A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ... This article or section does not cite any references or sources. ... This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... Paleontology, palaeontology or palæontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. ... Celestial mechanics is a division of astronomy dealing with the motions and gravitational effects of celestial objects. ... Orders & Suborders Saurischia Sauropodomorpha Theropoda Ornithischia Thyreophora Ornithopoda Marginocephalia Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. ... Binomial name Tyrannosaurus rex Osborn, 1905 Synonyms Manospondylus gigas Dynamosaurus imperiosus Dinotyrannus megagracilis Nanotyrannus lancensis? Tyrannosaurus (IPA pronunciation or ; from the Greek τυραννόσαυρος, meaning tyrant lizard) is a genus of tyrannosaurid theropod dinosaur. ... In astronomy, geology, and paleontology, mya is an acronym for million years ago and is used as a unit of time to denote length of time before the present. ... In astronomy, a Julian year is a unit of time defined as exactly 365. ... One thousand million (1,000,000,000) is the natural number following 999,999,999 and preceding 1,000,000,001. ... Physical cosmology, as a branch of astrophysics, is the study of the large-scale structure of the universe and is concerned with fundamental questions about its formation and evolution. ... This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... The long and short scales are two different numerical systems used throughout the world: Short scale is the English translation of the French term échelle courte. ... For other uses, see American English (disambiguation). ... Main article: Names of large numbers A quintillion is a number written as either: a 1 followed by 18 zeros (10 to the 18th power, as used in the short scale system of numeration. ... General Name, Symbol, Number tungsten, W, 74 Chemical series transition metals Group, Period, Block 6, 6, d Appearance grayish white, lustrous Standard atomic weight 183. ...

See also

• Before Present
• bya
• byr
• Geologic time scale
• Giga-annum or Ga
• kyr
• mya
• myr
• tya (sometimes spelled kya)
• Orders of magnitude (time)

Before Present (BP) years are the units of time (counted backwards to the past) used to report raw radiocarbon ages and dates referenced to the BP scale origin in the year AD 1950 (identical to 1950 CE). ... In [[hhehehe>12). ... Byr was often used in geology and astronomy as a unit of one billion years. ... // For other uses, see time scale. ... Giga-annum, usually abbreviated as Ga, is a unit of time equal to 10^9 years. ... GA ... kyr is occasionally used in geology and astronomy as a unit of one thousand years or millennium. ... In astronomy, geology, and paleontology, mya is an acronym for million years ago and is used as a unit of time to denote length of time before the present. ... Myr is often used in geology as a unit of one million years. ... For the R&B singer, see Mya (singer). ... The pages linked in the right-hand column contain lists of times that are of the same order of magnitude (power of ten). ...

References

1. ^ National Institute of Standards and Technology (NIST) Special Publication 811, Guide for the Use of the International System of Units (SI), (1995)
2. ^ International Organization for Standardization (ISO) 31-1, Quantities and units — Part 1: Space and time, Geneva, Switzerland (1992)