Prefixes in units of measurement
Prefixes derived from the Greek and Latin words for particular numbers occur in many different types of word in English - e.g., in words for units of measurement (such as 'millilitre' and 'centimetre') and in words for geometrical figures (such as 'pentagon' and 'tetrahedron').
The table below sets out the way in which prefixes derived from the Greek and Latin words for particular numbers function in words which denote units of measurement. For other numerical prefixes derived from Greek and Latin see Prefixes for very high numbers and Prefixes in words for geometrical figures.
Prefixes derived from the Greek and Latin words for the numbers 10, 100, and 1000 are most commonly found in combination with the words 'metre', 'gram', and 'litre' (the words for the basic units of, respectively, length, mass, and capacity); but they can also be combined with many other units of measurement. The prefixes derived from Greek produce multiples of the basic unit, i.e., units which are ten, a hundred, or a thousand times the basic unit, while the prefixes derived from Latin give fractions of the basic unit, i.e., units which are a tenth, an hundredth, or a thousandth of the basic unit.
Here are the details:
| Greek or Latin Number | Prefix and meaning | Unit of measurement | |
|---|---|---|---|
| chilioi (Greek 1000) | kilo-, 1000 | kilometre, kilogram, kilolitre | For notes on pronunciation and spelling see Kilometer - kilometre |
| hekaton (Greek, 100) | hecto- (before a vowel hect-), 100 | hectometre, hectogram, hectolitre | |
| deka (Greek, 10) | deca- or deka- (before a vowel dec- or dek-), 10 | decametre, decagram, decalitre | '-c-' pronounced 'hard', like '-k-' |
| decem (Latin, 10) | deci- (before a vowel de-), 1/10 | decimetre, decigram, decilitre | '-c-' pronounced 'soft', like '-s-' |
| centum (Latin, 100) | centi- (before a vowel cent-), 1/100 | centimetre, centigram, centilitre | |
| mille (Latin, 1000) | milli- (before a vowel mill-), 1/1000 | millimetre, milligram, millilitre |
Note that although the Latin-derived prefixes deci-, centi- and milli- usually signify fractions, viz., a tenth, an hundredth, and a thousandth (as in 'decibel', 'centigrade', 'millisecond', and 'millibar'), they can sometimes signify 10, 100, or 1000, respectively. Thus 'decennial' means 'lasting 10 years or occuring every 10 years'; a centipede is a creature with (roughly) 100 pairs of legs; and a millennium is a period of 1000 years.
