1. Deals the study of animals, including classification, physiology, development, and behavior (branches include: Entomology, Ethology, Herpetology, Ichthyology, Mammalogy, and Ornithology).
2. A branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct.
Word origin: From Ancient Greek ζῷον (zōon, “animal”) + λόγος (logos, “knowledge”).