Incorrect spelling

41th

Incorrect spelling, explanation: ordinal numbers have endings for their number forms taken from the word forms. This means the correct ending for forty-first is 41st (with st), not 41th. Th is used in numbers ending with such a sound. Therefore 41st is the only correct form here.


Correct spelling

41st

Correct spelling, explanation: 41st is the correct form, because it is written as the word forty-first, so st is the appropriate ending here. Th is an ending for numbers with such sound at the end, so 41th is incorrect. 41st is the only correct form.

Definition of 41st:
numeral, the ordinal number between 40th and 42nd
It’s my 41st birthday, but I feel 10 years younger!
My favorite thrift shop is on 41st Street.


Incorrect spelling

41nd

Incorrect spelling

Incorrect spelling

41rd

Incorrect spelling