Ordinal numbers tell us the position or order of something in a sequence. They answer the question “which one?” and are commonly used in speaking. Just as with cardinal numbers, these numbers were defined by mathematician Georg Cantor.
Think of them like this: if you’re in a race, you might come in first, second, or third place. Those “first,” “second,” and “third” are ordinal numbers.
Here are some key things about ordinal numbers:
- Position: They indicate the place of something in a list or order.
- Sequence: They show the order of items in a series.
- Examples: first, second, third, fourth, fifth, tenth, hundredth, and so on.
Difference between cardinal and ordinal numbers
It’s important to remember the difference between cardinal and ordinal numbers:
- Cardinal numbers: Tell us “how many” (e.g., 3 apples)
- Ordinal numbers: Tell us the position or order (e.g., the 3rd apple in the line)
How to write ordinal numbers
- In words: first, second, third, fourth, fifth, sixth, seventh, eighth, ninth
- In numerals: 1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, 9th
- For numbers 10 and above: you usually add “th” to the end of the cardinal number (e.g., 10th, 11th, 20th, 100th). There are some exceptions, like 21st, 22nd, and 23rd.
| Cardinal | Ordinal | |||
| 1 | One | 1st | First | |
| 2 | Two | 2nd | Second | |
| 3 | Three | 3rd | Third | |
| 4 | Four | 4th | Fourth | |
| 5 | Five | 5th | Fifth | |
| 6 | Six | 6th | Sixth | |
| 7 | Seven | 7th | Seventh | |
| 8 | Eight | 8th | Eighth | |
| 9 | Nine | 9th | Ninth | |
| 10 | Ten | 10th | Tenth | |
| 11 | Eleven | 11th | Eleventh | |
| 12 | Twelve | 12th | Twelfth | |
| 13 | Thirteen | 13th | Thirteenth | |
| 14 | Fourteen | 14th | Fourteenth | |
| 15 | Fifteen | 15th | Fifteenth | |
| 16 | Sixteen | 16th | Sixteenth | |
| 17 | Seventeen | 17th | Seventeenth | |
| 18 | Eighteen | 18th | Eighteenth | |
| 19 | Nineteen | 19th | Nineteenth | |
| 20 | Twenty | 20th | Twentieth | |
| 21 | Twenty-one | 21st | Twenty-first | |
| 22 | Twenty two | 22nd | Twenty-second | |
| 23 | Twenty-three | 23rd | Twenty-third | |
| 24 | Twenty-four | 24th | Twenty-fourth | |
| 25 | Twenty-five | 25th | Twenty-fifth | |
| … | … | … | … | |
| 30 | Thirty | 30th | Thirtieth | |
| 31 | Thirty-two | 31st | Thirty-first | |
| 32 | Thirty-three | 32nd | Thirty-second | |
| 33 | Thirty-four | 33rd | Thirty-third | |
| … | … | … | … | |
| 40 | Forty | 40th | Fortieth | |
| 50 | Fifty | 50th | Fiftieth | |
| 60 | Sixty | 60th | Sixtieth | |
| 70 | Seventy | 70th | Seventieth | |
| 80 | Eighty | 80th | Eightieth | |
| 90 | Ninety | 90th | Ninetieth | |
| 100 | One hundred | 100th | Hundredth | |
| … | … | … | … | |
| 1000 | One thousand | 1000th | Thousandth | |
[…] Ordinal numbers: When writing the day, we often use ordinal numbers (first, second, third, fourth, etc.). While you often say the ordinal, it’s becoming more common to just write the cardinal number (4 instead of 4th). Both are acceptable. […]