A theatregoer is someone who goes to see plays at the theatre, and does it regularly enough that it is part of who they are. It is not a job and not a skill — it just names the kind of person who buys tickets, reads reviews, and knows what is on this season. The word is a little formal, and you find it most in newspapers, reviews and in the language of the theatre business itself: 'theatregoers complained about the ticket prices'. In everyday conversation people would just say 'people who go to the theatre' or 'the audience'. Note that theatregoer is about the habit, while audience is about the people sitting in the room on one particular night — so all theatregoers are in an audience sometimes, but a tourist who wandered in once is part of the audience without being a theatregoer. English makes a lot of these -goer words the same way: churchgoer, cinema-goer, concert-goer, partygoer, and the very common one for sport, moviegoer in American English. British English spells it theatregoer; American English spells it theatergoer. Both forms appear with or without a hyphen, and both are fine.

常看戲的人、劇迷、（劇場的）觀眾群。跟一次性的 audience（現場觀眾）不同，theatregoer 講的是「有這個習慣的人」。