Correct spelling

23rd

Correct spelling, explanation: 23rd is the correct form because the word form of this number is twenty-third. As you can see such a form ends with rd sound so this should also be the sound added as a suffix to the numeral form. This rule applies to all ordinal numbers, for example, forty-sixth is 46th while eight hundred ninety-first is 891st. This is why 23rd is correct and 23th isn’t.

Definition of 23rd:
numeral, the ordinal number between 22nd and 24th
Jerry has a huge party for his 23rd birthday.
Mary loves Paris, it is her 23rd time there!


Incorrect spelling

23th

Incorrect spelling, explanation: this is an incorrect form of writing this ordinal number. This is because twenty-third (the full-word form) ends with rd, not th. We should add the same suffix to a number that the word form ends with. Hence twenty-third is 23rd, not 23th. This rule goes with all ordinal numbers. Therefore 23rd is the correct form.

Incorrect spelling

23nd

Incorrect spelling

Incorrect spelling

23st

Incorrect spelling