ID is short for identification, which means proof of who you are. An ID card typically shows your name, photo, birth date, and sometimes your address or other information. Adults carry driver's licenses or passports as ID. Students often have school IDs with their photo and grade.

You might need to show ID to check out library books, board an airplane, or prove your age. Security guards might ask to see your ID before letting you into a building.

When something is identified, it means someone has figured out what or who it is. Police might ID a suspect by matching fingerprints. Scientists ID new species by examining their unique features. In this sense, ID works as a verb: “Can you ID that bird?” means “Can you identify what kind of bird that is?”

The abbreviation is pronounced like two separate letters: “eye-DEE.”