Definitions for "Cepheid"
(variable star): a type of variable star that changes brightness by changing size and temperature with a period that depends on its average luminosity. More luminous Cepheids have longer pulsation periods. Cepheids are particularly valuable for determining distances to the nearby galaxies in which they reside. Distances to Cepheids are derived from measurements of their pulsation periods and apparent brightnesses and application of the inverse square law of light brightness.
a star orbited by a planet
a variable star whose intrinsic brightness is related to the period of its oscillations