What category is an Octopus in?

Question

For example a spider is an arachnid, what is an Octopus

Answer 1

They belong to the scientific order Octopoda.

If you don't know your scientific taxanomic nameing the main 7 groups are: Kingdom, Phylum, Class, Order, Family, Genus and Species. (In order from most broad to least). So following this "octupus" is a very broad term because as for humans the order we belong to is Primates.

PS. "biotechjones" answer cuts off at class. It is true a octupus is a part of the phylum Mollusca and class Cephalopoda but Cephalopoda includes squid and "cuttle fish" too.

Answer 2

Simple. Octopus is a Mollusc (Mollusk if you're a silly american) and more specifically a cephalopod!
Cephalo... means 'head' ...pod means 'foot'

So it's a 'head foot'! This make's sense, all of it's tentacles (called the foot for in mollusks) is on the front of it's face! Squids also fall in to this category as do the wildly beautiful Nautiluses! You may know other mollusks, like snails, slugs, clams, oysters and mussels! But all of these have shells right? So where's the octopus shell - it doesn't have one! It is almost entirely soft, so they can squeeze through tiny openings.