Correct spelling

81st

Correct spelling, explanation: this ordinal number appears after eighty and before eighty-two. The full form of 81st is eighty-first. The expression 81st comes from the Old English word ehta, which used to mean eight and had its origin in Germanic languages.

Definition of 81st:
1. number (ordinal) – a number that comes between eighty and eighty-two;
Over one hundred people took part in the marathon and John was the 81st, which wasn’t such a bad result.


Incorrect spelling

81th

Incorrect spelling, explanation: a common mistake made by many English users is to form the ordinal number 81st as 81th. The latter form is wrong as the -th ending is added to the most of ordinal numbers, except 1, 2, and 3. As ordinal numbers, they become the 1st, 2nd, and 3rd. Therefore, the only correct form is 81st.

Incorrect spelling

81rd

Incorrect spelling

Incorrect spelling

81nd

Incorrect spelling