English is not my native language, but looking at the French equivalent, wouldn't the choice of 'X is Y' or 'X are Y' be based on whether X is plural, as oppose

English is not my native language, but looking at the French equivalent, wouldn't the choice of 'X is Y' or 'X are Y' be based on whether X is plural, as opposed to Y ? "Bob is three kids in a trench coat" sounds better than "Bob are three kids in a trench coat" What's the rule for cases where it is not known whether X is singular or plural ? Phrases like "What we found" or "All I want for Christmas", for example. French grammar has several rules where, if a word must agree with a still unknown number or gender, then singular masculine is used: "J'ai mangé une pomme" vs. "La pomme que j'ai mangée" (the verb agrees with the apple only if the apple appears before it in the sentence). EDIT: I just realized that "All I want for Christmas" may actually be a plural, but "All I want for Christmas are a cookie" sounds strange...