Standby (theater)

An understudy is a theatrical term for someone who learns the lines and blocking/choreography of a leading actor or actress in a theatrical play. Should the lead actor or actress be unable to appear on stage because of illness or accident, the understudy takes over the part. Usually, when the understudy takes over, the theater manager will make the announcement prior to the start of the performance. Several actors made their name in show-business by being the understudy of a leading actor and taking the role over for several performances (for example, Anthony Hopkins with Sir Laurence Olivier).
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