"First thing, the first thing, a first thing, first things", what's different them?
Native speaker’s answer
Rebecca
Great question. The phrase "first thing" is used to mean early in the morning; before anything else. Ex: I usually check my phone first thing. The phrase "the first thing" is used to mean something you do before anything else. Ex: The first thing you should do in an exam is to read the question carefully. Neither "a first thing" nor "first thing's" are grammatically correct. I think you're getting confused with the article in "the first thing", but it cannot be replaced with "a". As for "first thing's" remember that apostrophe s represents ownership, so this would mean thing owns first which does not make grammatical sense. You may be confusing it with the idiom "first things first" which is often used to say that one should do the things that are most important before doing other things. Ex: I know you're eager to start shopping, but first things first—you need to figure out how much you can afford to spend.
