Cetacean comes from Latin cetus ('whale, large sea creature'), from Greek ketos ('sea monster, whale') + -acean. The historical trail runs through cetus in Latin and ketos in Ancient Greek. Morphologically, cetacean is transparent: it draws on Latin cetus ('whale, large sea creature'), from Greek ketos ('sea monster, whale') + -acean. Used as a noun and adjective, cetacean now means "a marine mammal of the order including whales, dolphins, and porpoises", so the present definition can be read against the older forms and meanings. The same lexical family is also visible in related forms such as cetology. The result is a borrowed or transmitted form whose modern spelling carries a compact record of its route into English.