The Latin root "aqua," found in words like "aquarium," means water. It appears in many English terms connected with water, including aquatic, aqueduct, aquaculture, and aqueous.
The Latin word aqua was a common feminine noun meaning water. English inherited many aqua-based terms through scientific, technical, and learned vocabulary rather than through everyday speech. In an aquarium, for example, water provides the environment for aquatic plants and animals.
An aqueduct is another clear example: the word combines aqua, meaning water, with ducere, meaning to lead. Roman aqueducts carried water over long distances to cities, where it supplied fountains, baths, and homes. Aquaculture similarly refers to the cultivation of aquatic organisms such as fish, shellfish, and algae.
The other options are roots with different meanings. Terra relates to earth, ignis to fire, and aer to air. "Aqua" can also describe a greenish-blue colour in modern English, but its original Latin meaning remains water.