Extra and Play-actor

Extra noun - An interchangeable part or piece of equipment that is kept on hand for replacement of an original.

Play-actor and extra are semantically related In some cases you can use "Play-actor" instead a noun "Extra".

Play-actor noun - An actor who travels around the country presenting plays.

Extra and play-actor are semantically related in actor topic. Sometimes you can use "Extra" instead a noun phrase "Play-actor", if it concerns topics such as person who performs.