Downstairs :: Downstairs (adv.) Down the stairs; to a lower floor.
Downstairs :: Downstairs (a.) Below stairs; as, a downstairs room..
Stair :: Stainlessly (adv.) In a stainless manner.
Stair :: Stair (n.) One step of a series for ascending or descending to a different level; -- commonly applied to those within a building.
Staircase :: Stair (n.) A series of steps, as for passing from one story of a house to another; -- commonly used in the plural; but originally used in the singular only..
Stairhead :: Staircase (n.) A flight of stairs with their supporting framework, casing, balusters, etc..
Stairway :: Stairhead (n.) The head or top of a staircase.
Understair :: Understair (a.) Of or pertaining to the kitchen, or the servants' quarters; hence, subordinate; menial..