The prefix com- (which also appears as con-, co-, col-, and cor-) often means “with” or “together.” It comes from Latin and shows up in hundreds of English words, usually indicating that things are being joined, done jointly, or happening at the same time.

When you cooperate with classmates on a project, you're working together. When you combine ingredients for cookies, you're bringing them together. A companion is someone you share bread with, which shows how the Romans thought about friendship.

The prefix changes its spelling to match the letter that follows it, making words easier to pronounce. It becomes con- in words like connect (link together) and conclude (bring to an end). It shortens to co- in coworker (someone who works with you) and co-author (someone who writes with you). It becomes col- before the letter L, as in collaborate (labor together) and collect (gather together). And it becomes cor- before R, as in correspond (exchange messages back and forth).

When you see this prefix, you're often looking at something that involves togetherness, whether it's people working jointly, things being joined, or actions happening at the same time.