Incorrect spelling

13rd

Incorrect spelling, explanation: 13rd is a mistake, because full-word form thirteenth ends with th, so the number form should also have suffix th. Therefore 13th is the correct form. rd is the suffix only for numbers with third at the end, for example twenty-third23rd.


Correct spelling

13th

Correct spelling, explanation: this is the correct way to write this number down, because full-word form ends with th (thirteenth; 13th). Only numbers ending with rd (so with third) have this suffix, for example 33rd, 963rd etc.). Therefore 13rd is incorrect and 13th is the correct form.

Definition of 13th:
numeral, ordinal number between 12th and 14th
It’s her 13th birthday today, so she is very excited.
The meeting is on April 13th.


Incorrect spelling

13st

Incorrect spelling

Incorrect spelling

13nd

Incorrect spelling