An actor (alternatively actress for a female; see terminology) is a person who acts in a dramatic or comic production and works in film, television, theatre, or radio in that capacity. The ancient Greek word for an "actor," ὑποκριτής (hypokrites), means literally "one who interprets"; in this sense, an actor is one who interprets a dramatic character.
A background actor or extra is a performer in a film, television show, stage, musical, opera or ballet production, who appears in a nonspeaking, nonsinging or nondancing capacity, usually in the background (for example, in an audience or busy street scene). War films and epic films often employ background actors in large numbers: some films have featured hundreds or even thousands of paid background actors as cast members (hence the term 'cast of thousands'). Likewise, grand opera can involve many background actors appearing in spectacular productions.
On a film or TV set, background actors are usually referred to as "background talent", "background performers", "background artists", "background cast members" or simply "background" while the term "extra" is rarely used. In a stage production, background actors are commonly referred to as "supernumeraries". In opera and ballet, they are called either "extras" or "supers".