You add the verb ''to be'' when there is a subject pronoun (I, you, he, she, it, we, they) ''He is stronger than I am.'' ''They are louder than we are.'' Another way to get around this problem is to change the subject pronoun to an object pronoun (me, you, him, her, us, them) "She is not more clever than HE IS. " -> "She is not more clever than HIM. " ''He is stronger than ME.'' ''They are louder than US.''