Iso 31-1

ISO 31-1 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to space and time. It was superseded in 2006 by ISO 80000-3.

Definitions

Its definitions include:

Quantity		Unit			Remarks
Name	Symbol	Name	Symbol	Definition	Remarks
angle, (plane angle)	α, β, γ, ϑ, φ	radian	rad	1 rad = 1 ^m⁄_m = 1
		degree	°	1° = ^π⁄₁₈₀ rad	There is no space between the number and these superscript-style unit symbols. Decimal subdivision of degrees is preferable (i.e., 12.5° instead of 12°30′)
		minute	′	1′ = (¹⁄₆₀)°
		second	″	1″ = (¹⁄₆₀)′
solid angle	Ω	steradian	sr	1 sr = 1 ^m²⁄_m² = 1
length	l, L	metre	m	The metre is the length of the path travelled by light in vacuum during a time interval of ¹⁄_{299 792 458} of a second; see speed of light
breadth	b
height	h
thickness	d, δ
radius	r, R
diameter	d, D
length of path, (linear) displacement vector	s, s
distance	d, r
cartesian coordinates	x, y, z
radius of curvature	ϱ
curvature	ϰ	reciprocal metre	m⁻¹		ϰ=¹⁄_ϱ
area	A	square metre	m²		The units are (1 a = 100 m²) and hectare (1 ha = 100 a) are used for agrarian areas.
volume	V	cubic metre	m³
volume	V	litre	L, l	1 L = 1 dm³	The capital L is preferred as the small l can be indistinguishable from the number 1 in some fonts.
time, time interval, duration	t	second	s	The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom	Representations of time of day are defined in ISO 8601.
		minute	min	1 min = 60 s
		hour	h	1 h = 60 min = 3 600 s
		day	d	1 d = 24 h = 86 400 s
angular velocity	ω	radian per second	^rad⁄_s		ω=^dφ⁄_dt
angular acceleration	α	radian per second squared	^rad⁄_s²		α=^dω⁄_dt
velocity	v (general symbol), v (velocity vector), c (propagation speed of waves), u, v, w (components of a velocity c)	metre per second	^m⁄_s
velocity		kilometre per hour	^km⁄_h
acceleration, acceleration vector	a, a	metre per second squared	^m⁄_s²	1 g = 9.80665 ^m⁄_s²
acceleration of free fall, acceleration due to gravity	g	metre per second squared	^m⁄_s²	1 g = 9.80665 ^m⁄_s²

Annex A

Annex A of ISO 31-1 lists units of space and time based on the foot, pound, and second.

Annex B

Annex B lists some other non-SI units of space and time, namely the gon, light year, astronomical unit, parsec, tropical year, and gal.

Time measurement and standards

Chronometry Orders of magnitude Metrology

International standards	UTC UTC offset UT ΔT DUT1 IERS ISO 31-1 ISO 8601 TAI 12-hour clock 24-hour clock Barycentric Coordinate Time Barycentric Dynamical Time Civil time Daylight saving time Geocentric Coordinate Time International Date Line Leap second New Earth Time Solar time Terrestrial Time Time zone

Obsolete standards	Ephemeris time Greenwich Mean Time Prime meridian

Time in physics	Absolute time and space Spacetime Chronon Continuous time Coordinate time Cosmological decade Discrete time Planck epoch Planck time Proper time Theory of relativity Time dilation Gravitational time dilation Time domain T-symmetry

Horology	Clock Astrarium Atomic clock Complication History of timekeeping devices Hourglass Marine chronometer Marine sandglass Radio clock Watch Water clock Sundial Dialing scales Equation of time History of sundials Sundial markup schema

Calendar	Astronomical Dominical letter Epact Equinox Gregorian Hebrew Hindu Intercalation Islamic Julian Leap year Lunar Lunisolar Solar Solstice Tropical year Weekday determination Weekday names

Archaeology and geology	Dating methodologies Geologic time scale International Commission on Stratigraphy

Astronomical chronology	Galactic year Nuclear timescale Precession Sidereal time

Units of time	Century Day Decade Fortnight Hour Jiffy Lustrum Millennium Minute Moment Month Paksha Saeculum Second Shake Tide Week Year

Related topics	Chronology Duration Mental chronometry Metric time System time Time value of money Timekeeper

ISO standards by standard number

List of ISO standards / ISO romanizations / IEC standards

1–9999	1 2 3 4 5 6 7 9 16 31 -0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 -13 128 216 217 226 228 233 259 269 302 306 428 518 519 639 -1 -2 -3 -5 -6 646 690 732 764 843 898 965 1000 1004 1007 1073-1 1413 1538 1745 1989 2014 2015 2022 2047 2108 2145 2146 2240 2281 2709 2711 2788 2852 3029 3103 3166 -1 -2 -3 3297 3307 3602 3864 3901 3977 4031 4157 4217 4909 5218 5428 5775 5776 5800 5964 6166 6344 6346 6385 6425 6429 6438 6523 6709 7001 7002 7098 7185 7200 7498 7736 7810 7811 7812 7813 7816 8000 8178 8217 8571 8583 8601 8632 8652 8691 8807 8820-5 8859 -1 -2 -3 -4 -5 -6 -7 -8 -8-I -9 -10 -11 -12 -13 -14 -15 -16 8879 9000/9001 9075 9126 9293 9241 9362 9407 9506 9529 9564 9594 9660 9897 9945 9984 9985 9995

10000–19999	10006 10116 10118-3 10160 10161 10165 10179 10206 10218 10303 -11 -21 -22 -28 -238 10383 10487 10585 10589 10646 10664 10746 10861 10957 10962 10967 11073 11170 11179 11404 11544 11783 11784 11785 11801 11898 11940 (-2) 11941 11941 (TR) 11992 12006 12182 12207 12234-2 13211 -1 -2 13216 13250 13399 13406-2 13407 13450 13485 13490 13567 13568 13584 13616 14000 14031 14224 14289 14396 14443 14496 -2 -3 -6 -10 -11 -12 -14 -17 -20 14644 -1 -2 -3 -4 -5 -6 -7 -8 -9 14649 14651 14698 -2 14750 14764 14882 14971 15022 15189 15288 15291 15292 15398 15408 15444 -3 15445 15438 15504 15511 15686 15693 15706 -2 15707 15897 15919 15924 15926 15926 WIP 15930 16023 16262 16612-2 16750 16949 (TS) 17024 17025 17203 17369 17799 18000 18004 18014 18245 18629 18916 19005 19011 19092 (-1 -2) 19114 19115 19125 19136 19439 19500 19501 19502 19503 19505 19506 19507 19508 19509 19510 19600 19752 19757 19770 19775-1 19794-5 19831

20000+	20000 20022 20121 21000 21047 21500 21827:2002 22000 23270 23271 23360 24517 24613 24617 24707 25178 25964 26000 26300 26324 27000 series 27000 27001:2005 27001:2013 27002 27003 27004 27005 27006 27007 27729 27799 28000 29110 29148 29199-2 29500 30170 31000 32000 38500 40500 42010 80000 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 -13 -14

Categories	ISO standards ISO 639 ISO 3166 ISO / IEC standards OSI protocols

Iso 31-1

Iso 31-1

Definitions

Annex A

Annex B

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