The nadir (/ˈneɪdɪər, -dər/, also UK: /ˈnædɪər/; Arabic: نظير, romanized: naẓīr, lit. 'counterpart') is the direction pointing directly below a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface. The direction opposite of the nadir is the zenith.