An
octopus ( or ; plural:
octopuses,
octopi, or
octopodes; see below) is a
cephalopod mollusc of the
order Octopoda. It has two eyes and four pairs of arms and, like other cephalopods, it is
bilaterally symmetric. An octopus has a
beak, with its mouth at the center point of the arms. An octopus has no internal or external skeleton (although some species have a vestigial remnant of a shell inside their
mantles), allowing it to squeeze through tight places. Octopuses are among the most intelligent and behaviorally diverse of all
invertebrates.