To form an ordinal number (ordinal numbers put things in order), add the ending -th to the cardinal number.

seven–>seventh

thirteen–>thirteenth

When a cardinal number ends in -y, the -y changes to -ie before adding -th.

twenty–>twentieth

sixty–>sixtieth

Note the following exceptions: first, second, third (sometimes abbreviated as 1st, 2nd, 3rd) and fifth, ninth, twelfth.

twenty-first

forty-third

sixty-fifth

All others are abbreviated as follows: 4th, 5th, 20th, etc.
 

Examples of Ordinal Numbers

• Take the elevator on the right to the seventh floor, and turn to your left after you exit the elevator.
• Is it on the first or second floor?