What does arcminute mean?
An arcminute is a unit for measuring angles, equal to one sixtieth of a degree — just as a minute of time is one sixtieth of an hour. Because a full circle contains 360 degrees, it contains 21,600 arcminutes, making each arcminute a very small slice of sky or horizon: about the width of a coin seen from several metres away. The term belongs mainly to technical fields such as astronomy, where it describes the apparent separation of celestial objects or the resolving power of telescopes; to navigation and surveying, where precise bearings matter; and to optometry and vision science, since a person with normal acuity can distinguish features about one arcminute across. It is usually written with the prime symbol (′) following a number, and sixty arcminutes make up one degree, while each arcminute divides further into sixty arcseconds. Precise, compact, and centuries old, the arcminute remains indispensable whenever small angles must be described clearly.
nounA unit of angular measurement equal to one sixtieth of a degree, used chiefly in astronomy, navigation, and optics.
- A unit of plane angular measurement equal to one sixtieth (1/60) of one degree.
"The telescope's resolution allowed it to distinguish objects just a few arcminutes apart."
"Venus and Jupiter appeared about ten arcminutes apart in the evening sky."
"Human vision can resolve details down to roughly one arcminute under good conditions."
Standard plural; sometimes shortened informally to 'arc mins' in technical speech.
"The full Moon spans about thirty arcminutes across the sky."
Your fingernail at arm's length spans roughly one arcminute — and that tiny sliver is how astronomers gauge the sharpness of the sharpest telescopes on Earth.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of arcminute
The word combines 'arc' — from Latin 'arcus', meaning bow or curve — with 'minute', from Medieval Latin 'minuta', short for 'pars minuta prima' ('first small part'), the classical subdivision of a degree or hour. The sexagesimal system of dividing circles into degrees, minutes, and seconds was inherited from ancient Babylonian astronomy via Greek and Arabic sources and became standard in European scientific writing by the early modern period. The explicit compound form 'arcminute' arose later, chiefly to distinguish the angular 'minute' from the unit of time. Its cognates include other 'minute'-derived terms such as 'minutia' and 'diminution', all tracing back to the Latin root 'minor' ('smaller').
How arcminute is actually used
Arcminute is a technical term used mainly in astronomy, geodesy, navigation, and optics; it is rarely encountered in everyday speech. It is often abbreviated with the prime symbol (′) after a numeral, e.g. 30′. The plural is normally 'arcminutes'.
Easily confused with arcminute
An arcsecond is one sixtieth of an arcminute, so it is a far smaller unit of angle.
A minute is a unit of time (or, as 'minute of arc', the same unit written without the 'arc' prefix); 'arcminute' specifically denotes the angular measure.