The word minute hides two different measurements. In an angle, a minute is an arcminute written with the prime sign ′. In time, a minute is written min.
The difference is especially easy to miss in astronomy, navigation, surveying, and mapping, where angles and durations can appear side by side. It becomes even easier to lose after a value is copied out of a table or map. Reading the whole expression is more reliable than relying on the shared English word.
Two meanings of “minute”
| If you mean… | Write | Relationship | Example |
|---|---|---|---|
| Plane angle | ′ | 1/60 of a degree | 15′ |
| Time | min | 60 seconds | 15 min |
How an arcminute is written
In angular measurement notation, one degree is divided into 60 arcminutes, and each arcminute is divided into 60 arcseconds. A coordinate such as 12° 34′ 56″ therefore means 12 degrees, 34 arcminutes, and 56 arcseconds.
The prime character is U+2032 PRIME. Unicode lists minutes and feet among its established uses. The same code point can therefore have different conventional meanings, but an angular value makes the arcminute reading clear.
In plane-angle notation, °, ′, and ″ sit directly against their numbers. An arcminute is therefore written 34′, with no gap before the prime mark.
How a minute of time is written
A minute of time uses the symbol min. The BIPM lists the minute as a non-SI unit of time with the relation 1 min = 60 s. Because min follows the ordinary number-and-unit formatting rule, a duration is written with a space: 15 min.
This gives a simple visual test. 15′ is an angular notation using a prime mark; 15 min is a duration. Writing a prime as a shortcut for minutes of time may occur informally, but it removes the distinction that the standard unit symbols provide.
The prime mark is not an apostrophe
The true prime ′ is U+2032. A straight keyboard apostrophe ‘ is U+0027, and the typographic right single quotation mark ’ is U+2019. Fonts can make these characters look similar, especially at small sizes, but they remain different Unicode characters.
If copied text contains a raised stroke and you need to identify the character itself, the existing guide to prime, apostrophe, and right single quote separates those code points before you interpret the measurement.
Why ′ can also mean feet
Prime notation is context-dependent. In a height such as 6′ 2″, the prime commonly represents feet and the double prime inches. In 12° 34′ 56″, the same two marks represent arcminutes and arcseconds.
Unicode encodes the prime characters, not a separate “arcminute character” and “foot character.” The surrounding quantity tells you what the mark means. A database field labelled latitude, for example, gives very different semantic context from a field labelled height.
Moving between DMS and decimal degrees
Angles do not have to be written in degrees, minutes, and seconds. 30° 30′ is the same angle as 30.5°, because 30 arcminutes is half a degree.
The SI Brochure generally prefers decimal subdivision of the degree, while noting established uses of degrees-minutes-seconds in fields such as navigation, cartography, astronomy, and very small-angle measurement. Converting between the two forms is a numerical operation. Simply replacing ′ with min would change the notation to a time unit rather than convert the angle.
Keeping angle and time data readable
Use ′ for arcminutes and min for minutes of time. Preserve the prime code point when exact Unicode text is available, and use a documented fallback only when a system is restricted to ASCII.
In tables, include the quantity or unit in the heading instead of relying on short values alone. A heading such as latitude (° ′ ″) or duration (min) makes the intended quantity clear even after a value is copied out of its original sentence.
For the next subdivision of angle, see Arcsecond ″ vs Second s. The same principle applies there: a shared word does not make two measurement symbols equivalent.
The contrast between 15′ and 15 min also shows how spacing carries information in measurement notation. Plane-angle symbols are a specific exception to the usual number-unit spacing rule, so the prime sits directly against the number. The time symbol min follows the ordinary rule and is separated by a space.
Whitespace is therefore useful evidence, not decoration. Removing every space can damage 15 min; inserting a space before every unit-like mark would incorrectly rewrite 34′. Cleanup rules need to know which notation they are handling.
When both meanings appear in one document
Astronomy shows why the word alone is not enough. A page can contain angular positions, elapsed times, and coordinate conventions that look superficially similar, so a parser should not decide from “minute” or from one raised stroke in isolation.
Use the field label and neighboring symbols together. A U+2032 value following degrees points strongly to arcminutes; a value written with min in a duration field points to time. The mark starts the interpretation, and context finishes it.