An aquarium is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aquatic reptiles, such as turtles, and aquatic plants. The term aquarium, coined by English naturalist Philip Henry Gosse, combines the Latin root aqua, meaning 'water', with the suffix -arium, meaning 'a place for relating to'.

A vivarium is an area, usually enclosed, for keeping and raising animals or plants for observation or research. Water-based vivaria may have open tops providing they are not connected to other water bodies. An animal enclosure is considered a vivarium only if it provides quality of life through naturalistic components such as ample living space and natural decor that allow and encourage natural behaviours. Often, a portion of the ecosystem for a particular species is simulated on a smaller scale, with controls for environmental conditions such as temperature, humidity and light.