John Larrysson Column: Counting Words (1 of 3)
Cardinals, Ordinals and Prefixes

This week I will talk about counting in English. Like almost all languages English counting is based on groups of ten. The three most common ways of counting in English are using cardinals, ordinals and prefixes. The word cardinal means very important. The cardinal numbers is simply how many objects there are.


There is only one China.



Seven million people live in Hong Kong.


audio 1

The ordinal numbers are those in order of succession. So an ordinal number is an adjective that describes what place an object has in a list.


That was my third piece of cake.



This is the seventh time I have been late for school.


While a cardinal number refers to several objects (three apples), an ordinal number refers only to one of those (the third apple). It is worth noting that there are only three words for ordinal numbers, first second and third. After that the ordinal numbers are derived from those cardinal numbers by adding a -th suffix. For example: He was emperor in the sixth dynasty. The first three words are repeated in the form twenty-first, twenty-second and so on.

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A prefix is part of a word that can be added at the front to create a new word. There are prefixes used to describe numbers that are particularly useful in science. However the prefixes above three are uncommon. For example, an icosahedron is a twenty sided object, using the prefix for twenty, icosa-. There is more than one prefix for each number because English has borrowed them from different languages (usually Latin or Greek). They can also be spelled differently.

Prefix Number Examples
semi, hemi, demi 1/2 western hemisphere (i.e. half a sphere), semisweet, demigod
uni 1 unicycle
bi, di 2 bicycle, dimethyl
tri, ter 3 tricycle, triangle, tercentenary (300th year)
tetra, tessera, quad 4









tetrachloride (a compound having 4 chlorine atoms), tesseract (4D-cube), a quadratic equation

penta, quin 5 pentagon, quintuplet
sex, hex 6 sextant (a navigation instrument using the sixth part of a circle), hexagon
hept, sept 7 heptane (C7H16), septuple (having seven parts), septuagenarian (age 70), September (before the addition of July and August it was the 7th month)
oct 8 octopus, October
non, nona, ennea 9 nonagenarian (90 years old), nonagon (nine side object, also called an enneagon)
dec, deca (deci-) 10(1/10)

decibel (a measure of sound based on log ten), decimetre (1/10 metre), December (see sept above), decade


Note: There are some uncommon metric measurements: deca=times ten, deci=one tenth, a decametre is ten meters, a decimetre is ten centimetres or 0.1 meters.

audio 3

There are other English counting words. These are words such as once, twice, thrice also single, double, triple and primary, secondary and tertiary. These number words have been called multiplicatives. Next week I will cover these other counting words.

audio 4

by John Larrysson

[email protected]

A native English speaker who has been teaching practical English in Hong Kong for more than a decade.