Incorrect spelling

41th

Incorrect spelling, explanation: suffix -th is used to create most ordinal numbers, however there are exceptions and one of them is -st. This suffix is added to number 1 and all other numbers containing one in them (for example 51, 111, 1091 etc.). Therefore ordinal number from number 41 is forty-first, so 41st. 41th is a mistake.


Correct spelling

41st

Correct spelling, explanation: 41st is the correct form, because cardinal number 41 ends with 1, therefore ordinal number ends with suffix consistent with it, which is -st. Usual suffix for ordinal numbers is -th, hence the mistake 41th, but there are three exceptions: 1st, 2nd and 3rd, therefore 41st is the right form of writing this number.

Definition of 41st:
numeral, ordinal number between 40th and 42nd
On the 41st anniversary of founding the school they organised an official ceremony.


Incorrect spelling

41nd

Incorrect spelling

Incorrect spelling

41rd

Incorrect spelling