A variable star whose variations arise for some external reason, such as rotation, orbital motion, or obscuration, as distinct from intrinsic processes such as pulsation. See Alpha2 Canum Venaticorum Star; BY Draconis Star; Eclipsing Binary; Ellipsoidal Variable; FK Comae Berenices Star; Intrinsic Variable; Magnetic Variable; Rotating Variable; SX Arietis Star.