A roster is an official list of people who belong to a group or team. Every sports team has a roster showing which players are on the team. Your teacher might keep a class roster with every student's name. A company maintains a roster of all its employees.

The word comes from the world of military organization, where commanders needed to track exactly which soldiers were assigned to their units. Today, you'll hear roster used whenever someone needs to keep track of who's part of a group: a baseball team announces its opening day roster, a band lists its current roster of musicians, or a scout troop maintains a roster of members.

When someone makes the roster, they've officially earned their spot on the team. Getting cut from the roster means being removed from the list. In workplaces, people sometimes work according to a duty roster, which shows who's scheduled to work on which days.

Notice that a roster is more official than just a casual list of names. Your birthday party invitation list isn't a roster, but the list of students enrolled in your school is. The word suggests organization, official membership, and keeping track of who belongs.