basement v. cellar

A basement is an entire floor of a building located partially or completely below ground level. A cellar is an underground room used for storage or shelter (e.g., a root cellar, wine cellar, or storm cellar). Basements are sometimes finished, habitable spaces; cellars often aren’t. A cellar can be constructed as a discrete structure, but a basement is always underneath a building’s ground floor. A cellar may be considered to be a type of basement, or a room within a basement, or the two terms may be used interchangeably.

Wikipedia on basement