octopus, plural octopuses or octopi, in general, any eight-armed cephalopod (octopod) mollusk of the order Octopoda. The true octopuses are members of the genus Octopus, a large group of widely distributed shallow-water cephalopods.

Why octopus is Mollusca?

These are mollusks with two shells that they can close up tight for protection. Finally there is Cephalopoda , the squids and octopuses. They only live in salt water, so we won't say much about them here. They have no shells, but are larger, smarter, and faster than their relatives in the other groups.

Is squid a Mollusca?

The members are known as molluscs or mollusks (/ˈmɒləsk/). ... Cephalopod molluscs, such as squid, cuttlefish, and octopuses, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest known invertebrate species.