To tag means to touch someone or something, usually as part of a game. In the playground game of tag, one person is “it” and tries to tag other players by touching them. Once you're tagged, you become the new “it” and chase the others.

The word also means to label or mark something for identification. When you tag your luggage before a trip, you attach a label with your name so it doesn't get lost. Scientists tag wild animals with small tracking devices to study where they travel. Online, you can tag friends in photos to show who's in them, or tag posts with keywords to help people find them later.

A tag can also be a noun: the physical label itself (like a price tag on clothing), or the small piece of fabric inside a shirt showing the brand and washing instructions. Kids sometimes cut these out because they're scratchy and annoying.

In graffiti, a tag is an artist's signature or symbol. Some cities have ongoing debates about whether tags are art or vandalism.

The phrase “tag along” means to follow someone, like when a younger sibling tags along on their older sibling's trip to the park.