Aqueous means of water, holding water, or like water. In science class the phrase you will see again and again is aqueous solution: a solid or a gas has been dissolved in water, so the water is the liquid that holds it. Chemists also talk about the aqueous layer in a tube — the watery part, as opposed to an oily part that will not mix. In the body, the aqueous humour is the clear watery fluid at the front of the eye. Though actually, outside the lab the word is rare; people just say watery or “in water.” It sounds technical and a little stiff, which is why textbooks love it. It does not mean “blue-green” (that is aqua as a colour) and it does not mean “related to the sea” in a loose holiday way.