动词 act 表示“扮演”的意思时，英语解释是：to perform in a play,film / movie , etc. 

        动词 play 表示“扮演”的意思时，英语解释是：to perform the actions and say the words of a particular character in a theatre perforemance , film etc. 

      【例句】

       Streep plays a shy, nervous woman.  斯特里普扮演一个腼腆、神经质的女人。

       Playing a character so different from herself was challenge. 扮演一个和她本人如此不同的角色是个挑战。

       I first started acting when I was 12 years old. 我12岁开始演戏。

       She is acting the role of Lady Macbeth six evenings a week. 她一星期六个晚上演麦克白夫人这个角色。       act the part / role of ... = play the part / role / character of ... （扮演......的角色）