Which is grammatically correct: We went to the movie before they? or We went to the movie before them?

Question

I would like to know which sentence is correct:  We went to the movies before they? or ...We went the movies before them.

Answer 1

First answer is “before them”. The reason is that “before them” is a prepositional phrase (preposition + noun), so the pronoun is the object of a preposition. Thus it needs to be the object form—“them”

 

There’s a second answer, for a second situation. “We went to the movies before they did”. In this case, “before” is still the preposition, but the object of the preposition is an entire clause (subject + verb). In this clause, the subject is in nominative case--“they”.