Ordinal Numbers
Ordinal numbers (first, second, third) tell us the position or order of something. We also use them in dates, centuries, and fractions.
- He lives on the third floor.
- It was my first accident.
- Jim was fifth in the competition.
- It's the eleventh of January. (dates, also written as: January 11th)
- There was a lot of poverty during the nineteenth century. (centuries)
- Use two thirds of a cup of milk. (fractions)
Forming ordinal numbers
The first three have special irregular forms:
- one → first (or 1st)
- two → second (or 2nd)
- three → third (or 3rd)
But most ordinal numbers are formed by adding -th to the cardinal number.
- four → fourth
- seven → seventh
- ten → tenth
- eleven → eleventh
- thirteen → thirteenth
- nineteen → nineteenth
- a hundred → hundredth
- a thousand → thousandth
Some have an irregular spelling:
| Cardinal | Ordinal | Rule |
|---|---|---|
| five | fifth | -ve becomes -f + -th |
| eight | eighth | |
| nine | ninth | |
| twelve | twelfth | -ve becomes -f + -th |
| twenty | twentieth | -y becomes -ie + -th |
| thirty | thirtieth | -y becomes -ie + -th |
For large compound numbers above twenty, only the last part changes into an ordinal number.
- Numbers ending in 1 → first (-st)
21 → twenty-first (21st) - Numbers ending in 2 → second (-nd)
32 → thirty-second (32nd) - Numbers ending in 3 → third (-rd)
43 → forty-third (43rd) - Most other numbers → -th
45 → forty-fifth (45th)
250 → two hundred and fiftieth (250th)
Watch out: 11, 12 and 13 always end in -th: 11th, 12th, 13th.
Quick reference
- cardinal numbers → one, two, three = how many
- ordinal numbers → first, second, third = position or order
- first, second, third
- fourth, fifth, eighth
- eleventh, twelfth, fifteenth
- twentieth, twenty-first, twenty-fifth
