Yes, the sentence is grammatically correct. It effectively defines the term actor and then provides additional context about gender preferences in terminology: "An actor is someone whose job is acting in plays or films. 'Actor' in the singular usually refers to a man, but some women who act prefer to be called 'actors' rather than 'actresses'." The sentence uses correct punctuation, and the clauses are logically connected. The phrase "in the singular" also clarifies the typical gendered use of actor when not referring to both men and women collectively, and it accurately describes the modern shift where actor is often used as a gender-neutral term.

Another word to add to your vocabulary bank: thespian = actor or actress.

Yes, the sentence is grammatically correct. It clearly explains the definition of an actor and notes the preference some women have for the term "actor" instead of "actress." The sentence structure and punctuation are appropriate, and the meaning is clear.

Perfect, and also very true factually. Well done.