After you
What it really means
Said when letting someone go first through a door, into a lift or into a queue. Polite refusal battles ("No, after YOU") are common and gently comic. Accepting with a "thank you" is perfectly fine.
Context, tips & common mistakes
"After you" yields a doorway, a queue spot or a lift exit, and it is one of the small ceremonies that keep British public space polite. The counter-move is 'no, after YOU', and the ping-pong can theoretically continue forever — the graceful resolution is for the second-invited person to accept with 'thanks very much' and go, because accepting a courtesy promptly is itself the courtesy.
Modern usage is gender-neutral and mostly about who reached the door first or who has hands full. Related rituals: holding a door for someone a few steps behind (they will do a small jog-trot of acknowledgement), and the held door 'thank you' which is close to mandatory — walking through a held door in silence is one of the fastest ways to be silently judged in Britain.