What does "stair" mean?

Stair: 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. "I a winding stair found." Chaucer's Dream. Below stairs, in the basement or lower part of a house, where the servants are. -- Flight of stairs, the stairs which make the whole ascent of a story. -- Pair of stairs, a set or flight of stairs. -- pair, in this phrase, having its old meaning of a set. See Pair, n., 1. -- Run of stars (Arch.), a single set of stairs, or section of a stairway, from one platform to the next. -- Stair rod, a rod, usually of metal, for holding a stair carpet to its place. -- Up stairs. See Upstairs in the Vocabulary.