Final answer:
The word 'celebrity' refers to a famous person, usually from the entertainment industry.
Step-by-step explanation:
The underline word in the sentence 'Yesterday, I saw a celebrity at the theater' is 'celebrity'. In this context, the word 'celebrity' refers to a famous person, usually from the entertainment industry. It could be a movie star, a singer, an actor, or any well-known public figure.
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