A cellar is a room built underground, usually beneath a house or building. Unlike a basement, which might be partly above ground with windows, a cellar sits entirely below ground level, surrounded by earth and typically reached by descending stairs.

Historically, people used cellars to store food because the earth keeps them naturally cool and dark, perfect for preserving vegetables, canned goods, and other supplies through the winter months. Before refrigerators existed, a cool cellar was essential for keeping food from spoiling. Wine collectors still use cellars (called wine cellars) for this reason: the steady, cool temperature protects wine as it ages.

The word can also mean a stock or collection of wines, as in “The restaurant has an excellent cellar with rare bottles from around the world.”

In older homes, especially farmhouses, you might find root cellars: small underground rooms designed specifically for storing potatoes, carrots, apples, and other crops. Some people also built storm cellars or cyclone cellars as safe spaces to shelter during tornadoes, since being underground provides protection from violent winds above.

Today, many cellars have been converted into extra living space, storage areas, or workshops, though they're still noticeably cooler than the rest of the house.