- Water, by its molecular formula, although rarely pure.
- (chemistry) A molecule of water.
- (inorganic chemistry) light water, consisting of two protium isotope of hydrogen atoms and one oxygen atom
- Water as a chemical substance.
- 1992, John R. Searle, The Rediscovery of the Mind, →ISBN, page 157:
- A man may believe, for example, that the star in the sky is the Morning Star without believing that it is the Evening Star. A man may, for example, want to drink a glass of water without wanting to drink a glass of H₂O.