How many or which one?
There are two jobs numbers do:
| Kind | Job | Examples |
|---|---|---|
| Cardinal number | Tells how many | one, two, three; 1, 2, 3 |
| Ordinal number | Tells position (which one) | first, second, third; 1st, 2nd, 3rd |
"I have three books" uses a cardinal number. "I’m reading the third book" uses an ordinal number.
Ordinal words and short forms
| Position | Word | Short form |
|---|---|---|
| 1 | first | 1st |
| 2 | second | 2nd |
| 3 | third | 3rd |
| 4 | fourth | 4th |
| 5 | fifth | 5th |
| 6 | sixth | 6th |
| 7 | seventh | 7th |
| 8 | eighth | 8th |
| 9 | ninth | 9th |
| 10 | tenth | 10th |
The letters after the numeral are called the suffix: -st, -nd, -rd or -th.
Suffix rules
- Numbers ending in 1 use -st (21st, 31st), except 11th.
- Numbers ending in 2 use -nd (22nd, 42nd), except 12th.
- Numbers ending in 3 use -rd (23rd, 53rd), except 13th.
- Everything else uses -th (4th, 15th, 100th).
The "teen" numbers 11, 12 and 13 are special: 11th, 12th, 13th.
Where we use ordinals
- Races: 1st, 2nd and 3rd place.
- Dates: July 1st, the 25th of December.
- Floors in a building: the 4th floor.
- Steps in instructions: first, second, then third.
- Birthdays: your 8th birthday.
Which way do you count?
Position depends on where you start. In a line facing a door, the person at the door is first. Always check: "first from the left" and "first from the right" can be different people. The order of the line is a sequence.
Worked examples
Example 1: In a line of runners, you are fourth. What is the short form?
Answer: 4th.
Example 2: Write the short form for twenty-second.
Ends in 2 (and isn’t 12): 22nd.
Example 3: Five children stand in a row: Ana, Ben, Cara, Dev, Eli. Who is third from the left?
Ana (1st), Ben (2nd), Cara (3rd).
Common mistakes
- Writing 2nd as "2th" or 3rd as "3th".
- Using -st, -nd, -rd for 11, 12, 13. They are 11th, 12th, 13th.
- Confusing ordinal and cardinal: "I came three in the race" should be "I came third".
Try it yourself
- Write the short form of "ninth".
- Write the short form of 31 as an ordinal.
- Which word is ordinal: "five" or "fifth"?
- In the row Ana, Ben, Cara, Dev, Eli, who is second from the right?
Answers: 1) 9th 2) 31st 3) fifth 4) Dev
Quick recap
- Ordinal numbers tell position; cardinal numbers tell how many.
- Suffixes: -st, -nd, -rd, -th; 11th, 12th, 13th are special.
- Always check where counting starts.