2rd

Incorrect spelling, explanation: 2rd is incorrect because rd is an indicator used with the number 3, not 2. There are two letters at the end of the word that indicates which the ordinal number is. For example, first – st, referring to 1, second – nd to 2, third – rd to 3, and so on. To sum up, rd indicates the third position of the object and it is incorrect together with figure 2. It should be joined with the number 3. And nd shows the second position, therefore 2nd is correct and 2rd is incorrect.

2nd

Correct spelling, explanation: Forming the ordinal number, the correct indicator is added to the figure. St following the number one, nd the number two, rd three and th the rest. The indicator consists of two letters that occur at the end of this ordinal, for example first – st, second – nd, third – rd, and so forth. It means that only 2nd is a correct form, not 2rd.

Definition of 2nd:
2nd – the ordinal number after the first and before the third,
My house is the 2nd on the left.
The letter B is the second in the alphabet.
In the 2nd year of their marriage, they have a baby.
Most people want to live on the 2nd floor.

2th

Incorrect spelling

2st

Incorrect spelling