What is the word that means a 'what if' phrase?

In a college course, I vaguely remember, the instructor wrote a word on the board that loosely meant or perhaps described any sentence that was a what-if statement. If I remember correctly it was essentially a word for classes of phrases, like say an appositive phrase. It was a more technical word, not something common like hypothetical, and for the life of me I can't recall it. Any help would be much appreciated.