A lineup is a group of people or things arranged in a row or sequence for a specific purpose.

In sports, the lineup is the list of players chosen to start a game. A baseball manager announces the batting lineup before the first pitch, deciding which nine players will play and in what order they'll bat. Basketball coaches set their starting lineup of five players. Getting into the starting lineup means you've earned your spot through practice and performance.

Police use lineups to help witnesses identify suspects. Several people stand in a row, and the witness tries to pick out the person they saw commit a crime. This process has to be fair: everyone in the lineup should look roughly similar so the witness can't be influenced by obvious differences.

The word also describes any group presented for viewing or selection. A store might display its lineup of new products. A music festival announces its lineup of performers. When your teacher asks everyone to line up for lunch, you're forming a line at the classroom door.

In each case, lineup suggests both organization and purpose. Things don't just happen to be next to each other. Someone arranged them that way for a reason, whether it's winning a game, solving a crime, or getting smoothly to the cafeteria.