Teuthology refers to the study of cephalopods, a class of marine animals that includes mollusks like octopuses, squids, and cuttlefish. Synonyms for teuthology include cephalopodology, the study of cephalopoda, and coleoidology, the study of coleoids (a subclass within cephalopoda that includes squids, cuttlefish, and octopuses). Other related terms include octopodology, the study of octopuses, and squidology, the study of squids. Teuthology is an important field of study because cephalopods are ecologically significant and complex animals that are vital to many marine ecosystems, yet are still not well understood in many ways.