Definition of "stairs"

At length, one night, when the company by ſome accident broke up much ſooner than ordinary, ſo that the candles were not half burnt out, ſhe was not able to reſiſt the temptation, but reſolved to have them ſome way or other. Accordingly, as ſoon as the hurry was over, and the ſervants, as ſhe thought, all gone to ſleep, ſhe ſtole out of her bed, and went down ſtairs, naked to her ſhift as ſhe was, with a deſign to ſteal them […]

1762, Charles Johnstone, The Reverie; or, A Flight to the Paradise of Fools‎, volume 2, Dublin: Printed by Dillon Chamberlaine, page 202

We tiptoed into the house, up the stairs and along the hall into the room where the Professor had been spending so much of his time.

1913, Joseph C. Lincoln, chapter 13, in Mr. Pratt's Patients