cycloid (sikloid)

and n. [= F. cycloïde = Sp. cicloíde = Pg. cycloide = It. cicloide, II. n. 1. A curve generated by a point in the circumference or on a radius of a circle when IMG:content-1911.jpg:[blocks in formation] the circle is rolled along a straight and ways in the same plane. When the point is in the circumference of the gener ating circle the curve generated is the common cycloid; when it is within the circle the curve is a prolate cycloid; and when it is on a radius produced beyond the circle the curve is a curtate cycloid. The cycloid is of great importance in relation to the theory of wave-motion. 2. In ichth., a cycloid fish; a fish with cycloid scales, or one of the Cycloidei. Companion to vertical line from the point of contact of a wheel rolling on a horizontal rail with a horizontal line from a fixed the cycloid, a curve described by the intersection of a point on the circumference of the wheel.