1. One of a group of highly luminous yellow or orange super giant stars, whose brightness varies in a regular manner as the result of stellar pulsations.
2. A yellow super giant star that varies regularly in brightness every few days or weeks as a result of pulsations.

The time that a Cepheid variable takes to pulsate is directly related to its average brightness; the longer the period, the brighter the star.

Cepheus is a constellation of the northern hemisphere near Cassiopeia (a W-shaped constellation in the northern hemisphere near Polaris) and Draco (a large faint constellation of the northern hemisphere).