attic

An attic is a floor level directly under a roof, where regular movement is impeded by the roof's shape. While it may be possible to walk upright through parts of an attic, the sloping or otherwise impinging roofline would prevent inhabitants from occupying the space as a regular floor.

The roof intrudes enough to prevent the level from functioning as a regular floor. Upright walking in one part does not exclude an attic when other areas remain restricted by the roof.

A top floor with adequate room for normal occupancy is not an attic merely because a roof lies above it. The roof's effect on usable space establishes the distinction.