In Greek mythology, a Cetus (Ancient Greek: Κῆτος, romanized: Kêtos) is a large sea monster. Perseus slew a cetus to save Andromeda from being sacrificed to it. The term cetacean (for whale) derives from cetus. In Greek art, ceti were depicted as serpentine fish. The name of the mythological figure Ceto is derived from kētos. The name of the constellation Cetus also derives from this word.