Play 和 act 皆可當名詞和動詞用，且都各有若干相當常見的意思。但本文僅討論這兩個字意思相近的部分，也就是兩者意為「(在戲劇和電影中) 扮演，演出」的動詞用法。就此用法而言，兩者皆可用作及物和不及物動詞。
然而，當及物動詞時，play 可直接接具名或不具名的角色當受詞，但 act 則不行。Act 須接 the part/role of + 具名或不具名的角色。另外，play 亦可接 the part/role of + 具名或不具名的角色，此時 play 和 act 為同義詞。必須注意的是，play 不可接戲劇或電影當受詞。例如：
- He played Hamlet at the Royal Theater last night. (昨晚他在皇家劇院扮演哈姆雷特) (正)
He acted Hamlet at the Royal Theater last night. (誤)
He acted (or played) the part/role of Hamlet at the Royal Theater last night. (正) - Who played Othello? (誰扮演奧賽羅？) (正)
Who acted Othello? (誤)
Who acted (or played) the part/role of Othello? (正) - She played Blanche in A Streetcar Named Desire. (她曾在《慾望街車》中扮演布蘭奇) (正)
- In the movie version, Vincent played the hero. (在電影版中，文森特扮演主人翁) (正)
- Paul was chosen to act the part of the lawyer in the film. (保羅被選中在影片中扮演律師的角色) (正)
- Marlon acted the part of Joseph. (馬龍扮演約瑟夫這個角色) (正)
- Sophia played over 30 TV plays. (索菲雅演過逾 30 齣電視戲) (誤) － plays 為名詞，意為「戲劇」。
Play 也經常用於被動態。例如：
- (The part/role of) Macbeth was played by Benjamin. (班傑明扮演馬克白 (的角色))
- The role of the mother was played by one of the British finest actresses. (那個母親的角色是由英國最出色的女星之一所扮演)
Play 和 act 亦可當不及物動詞用。例如：
- Benjamin is playing in King Lear at the National Theater. (班傑明將在國家劇院演出的《李爾王》一劇中軋一角)
- Oliver is acting (the part/role of Othello) tonight. (奧利佛今晚將表演 (奧賽羅的角色))
- I was asked to play in a new version of Shakespeare’s Hamlet. (有人請我去參加新版莎士比亞戲劇《哈姆雷特》的演出)
- Have you ever acted in a play before? (你以前演過戲劇嗎？)
- Sophia acted in over 30 TV plays. (索菲雅演過逾 30 齣電視戲)