<p><strong>Adverb</strong></p><ul><li>down the stairs.</li><li>to or on a lower floor.</li></ul><p><strong>Adjective</strong></p><ul><li>Also downstair.</li><li>pertaining to or situated on a lower floor, especially the ground floor.</li></ul><p><strong>Noun</strong></p><ul><li>(used with a singular verb) the lower floor or floors of a building: The downstairs is being painted.</li><li>the stairway designated for use by people descending: Don't try to go up the downstairs.</li></ul>