Term of the Moment: first cover, second cover

first cover--an actor paid to cover the star of a show, who may have no role of their own in the show. If so, they are a standby, meaning they are required to be available for every performance to cover the star, to be on standby. The standby is a principal contract and can only be on standby for principals in the show. (A standby may cover multiple principals. Sometimes by contract, the standby must be within a 15-minute walk of the theater while the performance is on.  A second cover is often an ensemble member who is rehearsed to cover the star role when the first cover is sick or on vacation.