The **minute** is a unit of time usually equal to 1/60 (the first sexagesimal fraction^{ [1] }) of an hour, or 60 seconds. In the UTC time standard, a minute on rare occasions has 61 seconds, a consequence of leap seconds (there is a provision to insert a negative leap second, which would result in a 59-second minute, but this has never happened in more than 40 years under this system). Although not an SI unit, the minute is accepted for use with SI units.^{ [2] } The SI symbol for *minute* or *minutes* is **min** (without a dot). The prime symbol is also sometimes used informally to denote minutes of time.^{ [3] }

Al-Biruni first subdivided the hour sexagesimally into minutes, seconds, thirds and fourths in 1000 CE while discussing Jewish months.^{ [4] }

Historically, the word "minute" comes from the Latin *pars minuta prima*, meaning "first small part". This division of the hour can be further refined with a "second small part" (Latin: *pars minuta secunda*), and this is where the word "second" comes from. For even further refinement, the term "third" (1⁄60 of a second) remains in some languages, for example Polish (*tercja*)^{[ citation needed ]} and Turkish (*salise*), although most modern usage subdivides seconds by using decimals. The symbol notation of the prime for minutes and double prime for seconds can be seen as indicating the first and second cut of the hour (similar to how the foot is the first cut of the yard or perhaps chain, with inches as the second cut). In 1267, the medieval scientist Roger Bacon, writing in Latin, defined the division of time between full moons as a number of hours, minutes, seconds, thirds, and fourths (*horae*, *minuta*, *secunda*, *tertia*, and *quarta*) after noon on specified calendar dates.^{ [5] } The introduction of the minute hand into watches was possible only after the invention of the hairspring by Thomas Tompion, an English watchmaker, in 1675.^{ [6] }

- ↑ "What is the origin of hours, minutes and seconds?".
*Wisteme*. Archived from the original on 24 March 2012. Retrieved 2011-05-25.What we now call a minute derives from the first fractional sexagesimal place

. - ↑ "Non-SI units accepted for use with the SI, and units based on fundamental constants".
*Bureau International de Poids et Mesures*. Archived from the original on 2014-11-11. Retrieved 2011-05-25. - ↑ Nelson, D. (2008). "Prime symbol (accent)".
*The Penguin Dictionary of Mathematics*(4th ed.). Penguin UK. ISBN 978-0-141-92087-0. - ↑ Al-Biruni (1879) [1000].
*The Chronology of Ancient Nations*. Translated by Sachau, C. Edward. pp. 147–149. - ↑ R Bacon (2000) [1928].
*The Opus Majus of Roger Bacon*. BR Belle. University of Pennsylvania Press. table facing page 231. ISBN 978-1-85506-856-8. - ↑ Mitman, Carl (1926). "The Story of Timekeeping".
*The Scientific Monthly*.**22**(5): 424–427. Bibcode:1926SciMo..22..424M. JSTOR 7652.

- Henry Campbell Black, Black's Law Dictionary, 6th Edition, entry on Minute. West Publishing Company, St. Paul, Minnesota, 1991.
- Eric W. Weisstein. "Arc Minute." From MathWorld—A Wolfram

A **minute of arc**, **arcminute** (arcmin), **arc minute**, or **minute arc**, denoted by the symbol ′, is a unit of angular measurement equal to 1/60 of one degree. Since one degree is 1/360 of a turn, one minute of arc is 1/21600 of a turn. The nautical mile (nmi) was originally defined as the arc length of a minute of latitude on a spherical Earth, so the actual Earth circumference is very near 21600 nmi. A minute of arc is π/10800 of a radian.

The word **day** has a number of meanings, depending on the context it is used such as of astronomy, physics, and various calendar systems.

An **hour** is a unit of time conventionally reckoned as 1⁄24 of a day and scientifically reckoned as 3,599–3,601 seconds, depending on conditions. There are 60 minutes in an hour, and 24 hours in a day.

A **leap second** is a one-second adjustment that is occasionally applied to Coordinated Universal Time (UTC), to accommodate the difference between precise time and imprecise observed solar time (UT1), which varies due to irregularities and long-term slowdown in the Earth's rotation. The UTC time standard, widely used for international timekeeping and as the reference for civil time in most countries, uses TAI and consequently would run ahead of observed solar time unless it is reset to UT1 as needed. The leap second facility exists to provide this adjustment.

The **second** is the base unit of time in the International System of Units (SI), commonly understood and historically defined as 1⁄86400 of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each. Analog clocks and watches often have sixty tick marks on their faces, representing seconds, and a "second hand" to mark the passage of time in seconds. Digital clocks and watches often have a two-digit seconds counter. The second is also part of several other units of measurement like meters per second for speed, meters per second per second for acceleration, and cycles per second for frequency.

A **metric prefix** is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The prefix *kilo-*, for example, may be added to *gram* to indicate *multiplication* by one thousand: one kilogram is equal to one thousand grams. The prefix *milli-*, likewise, may be added to *metre* to indicate *division* by one thousand; one millimetre is equal to one thousandth of a metre.

A **year** or **annum** is the orbital period of a planetary body, for example, the Earth, moving in its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the planet, four seasons are generally recognized: spring, summer, autumn and winter. In tropical and subtropical regions, several geographical sectors do not present defined seasons; but in the seasonal tropics, the annual wet and dry seasons are recognized and tracked.

A **microsecond** is an SI unit of time equal to one millionth of a second. Its symbol is **μs**, sometimes simplified to **us** when Unicode is not available.

**Metric time** is the measure of time intervals using the metric system. The modern SI system defines the second as the base unit of time, and forms multiples and submultiples with metric prefixes such as kiloseconds and milliseconds. Other units of time – minute, hour, and day – are accepted for use with SI, but are not part of it. Metric time is a measure of time intervals, while decimal time is a means of recording time of day.

**Sexagesimal**, also known as **base 60** or **sexagenary**, is a numeral system with sixty as its base. It originated with the ancient Sumerians in the 3rd millennium BC, was passed down to the ancient Babylonians, and is still used—in a modified form—for measuring time, angles, and geographic coordinates.

**Assyro-Chaldean Babylonian cuneiform numerals** were written in cuneiform, using a wedge-tipped reed stylus to make a mark on a soft clay tablet which would be exposed in the sun to harden to create a permanent record.

An order of magnitude of time is usually a decimal prefix or decimal order-of-magnitude quantity together with a base unit of time, like a microsecond or a million years. In some cases, the order of magnitude may be implied, like a "second" or "year". In other cases, the quantity name implies the base unit, like "century". In most cases, the base unit is seconds or years.

**60** (**sixty**) is the natural number following 59 and preceding 61. Being three times 20, it is called *threescore* in older literature.

**ISO 6709**, *Standard representation of geographic point location by coordinates*, is the international standard for representation of latitude, longitude and altitude for geographic point locations.

A **degree**, usually denoted by **°**, is a measurement of a plane angle in which one full rotation is 360 degrees.

**Decimal time** is the representation of the time of day using units which are decimally related. This term is often used specifically to refer to the time system used in France for a few years beginning in 1792 during the French Revolution, which divided the day into 10 decimal hours, each decimal hour into 100 decimal minutes and each decimal minute into 100 decimal seconds, as opposed to the more familiar UTC time standard, which divides the day into 24 hours, each hour into 60 minutes and each minute into 60 seconds.

A **unit of time** is any particular time interval, used as a standard way of measuring or expressing duration. The base unit of time in the International System of Units (SI) and by extension most of the Western world, is the second, defined as about 9 billion oscillations of the caesium atom. The exact modern definition, from the National Institute of Standards and Technology is: "The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the cesium frequency, Δ*ν*_{Cs}, the unperturbed ground-state hyperfine transition frequency of the cesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s^{−1}."

A **moment** (*momentum*) is a medieval unit of time. The movement of a shadow on a sundial covered 40 moments in a solar hour, a twelfth of the period between sunrise and sunset. The length of a solar hour depended on the length of the day, which, in turn, varied with the season. Although the length of a moment in modern seconds was therefore not fixed, on average, a moment corresponded to 90 seconds. A solar day can be divided into 24 hours of either equal or unequal lengths, the former being called natural or equinoctial, and the latter artificial. The hour was divided into four *puncta* (quarter-hours), ten *minuta*, or 40 *momenta*.

**Coordinated Universal Time** or **UTC** is the primary time standard by which the world regulates clocks and time. It is within about 1 second of mean solar time at 0° longitude such as UT1 and is not adjusted for daylight saving time. It is effectively a successor to Greenwich Mean Time (GMT).

**Sol** is a solar day on Mars; that is, a **Mars-day**. A sol is the apparent interval between two successive returns of the Sun to the same meridian as seen by an observer on Mars. It is one of several units for timekeeping on Mars.

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