animal without a vertebral column

An invertebrate is an animal that does not have a spinal column or backbone. This contrasts with vertebrate: if an animal is not a vertebrate (fish, reptile, amphibian, bird, or mammal), it is an invertebrate. Most animals, and most species of animal, are invertebrates.

A spider

The main phyla (groups) of invertebrate animals are:

Insects and other arthropods have no bones, but they have a skeleton on the outside of their bodies, called an exoskeleton.

There are 18 more groups of invertebrates, mostly minor: see List of animal phyla.