Definition: The word "invertebr" is a Latin term meaning "not vertebrate," and it originally referred to any type of invertebrate, such as insects or spiders. A vertebrate animal is one that has a backbone and spine, including mammals, reptiles, birds, fish, and amphibians. In contrast, an invertebrate animal does not have a backbone but instead uses only the skeletons of its body segments as a platform for its internal organs and other structures. Therefore, the word "invertebr" refers to any type of animal that lacks a vertebral column or spine and has no backbone. This includes all animals classified as invertebrates (like insects, spiders, and some fungi) and those that lack a backbone but use only skeletons for their internal organs and other structures (like certain fish). In biology, the term "invertebrate" is used to refer to any animal that lacks a vertebral column and has no backbone or spinal cord. It can also refer to a group of invertebrates that are classified as belonging to the same order or family (e.g., the group of crabs).