Zoology (also known as animal science) is the branch of biology devoted to the study of animal life. It covers areas ranging from the structure of organisms to the subcellular unit of life. Some zoologists are interested in the biology of particular groups of animals. Others are concerned with the structure and function of animal bodies. Still others study how new animals are formed and how their characteristics are passed on from one generation to another. Zoologists study the interactions of animals with one another and their environments, as well as the significance of the behavior of animals.

Zoology is both descriptive and analytical. It can be approached either as a basic science or as an applied science. A worker in basic zoology is interested in knowledge of animals for its own sake without consideration of the direct application of the information gained. In contrast, workers in applied zoology are interested in information that will directly benefit humans and animals (medicine, for example).

Historically, the study of zoology can be viewed as a series of efforts to analyze and classify animals. The ancient Greek philosopher Aristotle is credited with devising the system of classifying animals that recognized similarities among diverse organisms in the fourth century B.C.E.; he arranged groups of animals according to mode of reproduction and habitat. Zoology began to emerge as a science in the 12th century and long was dominated by studies of anatomy and efforts at classifying animals. The Swedish botanist Carolus Linnaeus developed a system of nomenclature that still is used today — the binomial system of genus and species — and established as a discipline taxonomy, the science of classification according to a predetermined system.

Zoology today is as diverse as the animal kingdom it studies, broadening its range to include such fields as genetics and biochemistry. It now is considered an interdisciplinary field that applies a great variety of techniques to obtain knowledge of the animal kingdom. For instance, the genetic study of DNA from various animals can provide insights into their evolutionary history. Zoologists who concentrate on the morphology (the study of structure, including muscles, bones, cells and cellular components) employ many techniques first developed in the biochemistry lab.