The correct way to write it is “12th”.
Ordinal numbers like 12th are formed by adding “th” to the cardinal number 12. The form “12nd” is not correct; it’s a mistake, as “nd” is used for numbers like 2nd, not for 12.
So, you would say “12th grade” or “on the 12th of January,” for example.
The use of “th”, “st”, “nd”, and “rd” in ordinal numbers depends on the number they modify. Here’s a more detailed breakdown:
General Rules for Ordinal Numbers:
- “st” is used for numbers ending in 1, except for 11.
- Examples: 1st, 21st, 31st, etc.
- Exceptions: 11th, 111th, 1001st (the “st” rule doesn’t apply to numbers ending in 11).
- “nd” is used for numbers ending in 2, except for 12.
- Examples: 2nd, 22nd, 32nd, etc.
- Exceptions: 12th, 112th, 1002nd (the “nd” rule doesn’t apply to numbers ending in 12).
- “rd” is used for numbers ending in 3, except for 13.
- Examples: 3rd, 23rd, 33rd, etc.
- Exceptions: 13th, 113th, 1003rd (the “rd” rule doesn’t apply to numbers ending in 13).
- “th” is used for all other numbers, including those ending in 4 through 9, and for 10, 11, 12, 13, and so on.
- Examples: 4th, 5th, 6th, 7th, 8th, 9th, 10th, 11th, 12th, 13th, etc.
Specific to 12th:
- The number 12 ends in “2”, but since it falls within the exception range (12, 112, etc.), the correct ordinal is 12th.
- Even though 12 ends in a “2,” it does not get the “nd” suffix (which is used for 2nd, 22nd, 32nd) because of the exception rule. So, “12nd” is incorrect.
Examples:
- 1st: First
- 2nd: Second
- 3rd: Third
- 4th: Fourth
- 12th: Twelfth (even though 12 ends in “2”, it follows the general “th” pattern for numbers like 10th, 11th, etc.)
This is the rule applied in both written and spoken English to show the position or rank in a sequence.
