A gate is an opening in a fence or wall that can be closed to control who or what passes through. Unlike a door in a building, a gate typically guards an outdoor space: a backyard, a farm, a garden, or an entire property. Gates swing open to let people, animals, or vehicles pass, then close to keep them in or out.

The word also appears in many compound terms. At an airport, each boarding gate is where passengers wait before entering their airplane. A gateway can be a literal entrance, like the grand gateway to a park, or something that opens up new possibilities: learning to read is often called a gateway to knowledge. In sports, a tailgate party happens in a parking lot before a game, named after the hinged back panel (the tailgate) of a pickup truck that folds down to create a convenient table or seat.

Gates serve both practical and symbolic purposes. A locked gate provides security and privacy. An open gate signals welcome. Throughout history, city gates controlled who entered walled towns, and guards would close them at night for protection. When someone says they're “at the gate” of something new, they mean they're right on the threshold of a new opportunity or experience.