1. (n.) A portion of a curved line; as, the arc of a circle or of an ellipse.

2. (n.) A curvature in the shape of a circular arc or an arch; as, the colored arc (the rainbow); the arc of Hadley's quadrant.

3. (n.) An arch.

4. (n.) The apparent arc described, above or below the horizon, by the sun or other celestial body. The diurnal arc is described during the daytime, the nocturnal arc during the night.

AC arc Poulsen arc aperiodic discharge arc column arc discharge arc light arch bend bow brush discharge catacaustic catenary caustic circle color filter conchoid crook curl curvation curvature curve diacaustic dimmer discharge disruptive discharge electric discharge electric shock electric spark electrodeless discharge ellipse festoon floats flood floodlight footlights foots galvanic shock gelatin glow discharge hook hyperbola klieg light light plot lights limelight lituus marquee medium oscillatory discharge parabola round shock silent discharge sinus spark spark gap spot spotlight tracery