An ordinal number serves as an adjective when it modifies a noun. Look at these examples.
My sister is in the first grade.
David was the second person to win the lottery in our town.
I live in the third house from the corner.
Use an ordinal number as an adjective when it modifies a noun in the sentence.
It’s your turn. Find the ordinal number in this sentence that is used as an adjective. This is our fifth game in a week. Did you find it? Good for you!