a tank or pool or bowl filled with water for keeping live fish and underwater animals
"The children spent hours watching the colorful fish swim in the large aquarium at the museum."
A tank, often made of glass, for keeping live fish or other aquatic animals.
"The children gathered around the large aquarium to watch the colorful fish swim among the coral."
In plain English: An aquarium is a glass tank filled with water where people keep fish and other sea creatures to watch them swim around.
"The children spent hours feeding the fish in their new aquarium."
Usage: An aquarium refers specifically to the physical container used to house aquatic life rather than the hobby itself. Use this term when describing a home setup with tanks and equipment instead of general terms like "fish bowl" if you are referring to larger, more complex systems.
The word aquarium comes from the Latin aquārium, meaning "of or pertaining to water." It entered English either directly from this root or possibly through a 19th-century blend created by naturalist Philip Henry Gosse combining aquatic and vivarium.