A lavatory is a room with a toilet and sink, or sometimes just the toilet itself. The word sounds formal because it comes from Latin words meaning “to wash,” but people use it in everyday situations. On an airplane, the small bathroom is called a lavatory. In older schools or public buildings, you might see signs pointing to the lavatories instead of restrooms or bathrooms.

In modern use, especially in Britain and on airplanes, lavatory typically refers to the whole bathroom.

You might wonder why we need so many words for the same room: bathroom, restroom, washroom, lavatory, toilet, WC (water closet). Different words feel right in different settings. Lavatory sounds more formal and technical, so you'll hear it more often in public places, on vehicles, or in official contexts. At home, most people just say bathroom.