Squid are cephalopods of myopsida and oesopsida, which were previously considered to be two suborders of teuthida, but recent studies show that teuthida is symbiotic. There are about 304 kinds of current two orders. Like all cephalopods, squid has a unique head, bilateral symmetry, Cape and arms. Squid, like squid, has eight arms arranged in pairs and two usually longer tentacles.

Squid is a member of the cephalopod and colleoidea subclasses, which are myopsida and oesopsida (including giant squid such as Architeuthis Dux). An effective authidae may be the largest Cephalopoda, with about 300 species divided into 29 families.

Orders from myopsida and oesopsida are classified as superdecapods (from Greek for "ten feet"). The other two orders of Decapoda cephalopods are also called squid, although they are different from squid in taxonomy and can be recognized in general anatomical characteristics. They are the short tailed squid of sepiolida the and the ram horn squid in the shape of spirulida mono. However, vampire squid and octopus are more closely related than any squid.