An ordinal number is a number that shows order. An ordinal number modifies a noun and acts as an adjective when it comes just before the noun. Look at these sentence examples:
Jane is in sixth grade.
My little sister lost her first tooth.
Joseph scored his third goal in the soccer game yesterday.
Susan’s parents are celebrating their twenty-fifth anniversary.
An ordinal number is an adjective. An ordinal number modifies a noun when it comes right before the noun.
▶It’s your turn. Find the ordinal number that acts as an adjective in this sentence: December is the twelfth month of the year. Did you find the ordinal number? Good for you!