Cellar

A cellar is a story with more than half its height below the curb level or adjoining grade, distinguishing it from a basement, which sits at least half above. The distinction is not pedantry: cellar space is generally excluded from zoning floor area, so it does not consume the lot's FAR budget — which is why dense buildings push storage, mechanical space, and back-of-house functions below grade.

What a cellar may be used for is a separate question governed by housing, building, and fire rules, and the distinction between lawful cellar uses and unlawful cellar dwellings is a recurring enforcement subject. Zoning's cheap square footage is not automatically habitable square footage.