What does aqueous mean?
Aqueous is an adjective meaning relating to, containing, or dissolved in water. Its most common use is in chemistry, where an aqueous solution is one in which water serves as the solvent — as opposed to solutions made with other liquids such as alcohol or acetone. The word also appears in biology and medicine: the aqueous humor is the clear, watery fluid that fills the space between the cornea and the lens of the eye. Beyond these technical contexts, aqueous can describe anything watery in character, such as a thin, dilute liquid. The term derives from the Latin aqua, meaning water, and shares this root with words like aquatic, aqueduct, and aquifer. Because it signals precision about what a liquid actually contains, aqueous is an essential word in laboratory science, pharmaceutical labeling, and any field where the distinction between water-based and other liquid systems matters.
adjectiveOf, relating to, or containing water; especially denoting a solution in which water is the solvent.
- Relating to, containing, or dissolved in water — most commonly used in chemistry to describe solutions in which water is the solvent.
- Resembling or having the qualities of water, such as being watery or diluted in appearance or consistency.
"The chemist prepared an aqueous solution of sodium chloride for the titration."
"Copper sulfate dissolves readily to form a blue aqueous solution."
"The paint's aqueous base made it easy to clean up with soap and water."
The clear fluid filling the front of your eye is literally called the 'aqueous humor' — you are carrying a tiny aqueous solution around with you at all times.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of aqueous
Aqueous comes from the Latin aqua, meaning water, entering English in the mid-17th century through New Latin usage in chemistry and alchemy. It is closely related to the Medieval Latin adjective aquosus, meaning watery. The same Latin root gives rise to a family of English words including aquatic, aqueduct, aquifer, and aquamarine, all of which retain a direct connection to water in their meanings.
How aqueous is actually used
Aqueous is primarily a technical term used in chemistry, biology, and medicine, though it appears in general scientific writing. It carries a formal register and is rarely used in casual conversation. In chemistry, 'aqueous' specifically signals that water is the solvent, distinguishing it from non-aqueous solvents like ethanol or acetone.
Easily confused with aqueous
Aquatic describes things that live in or relate to water as a habitat (like aquatic plants), while aqueous describes substances that contain or are dissolved in water.