- the acid, H2CO3, formed when carbon dioxide dissolves in water, known in the form of its salts and esters, the carbonates.
- a weak acid formed when carbon dioxide combines with water: obtained only in aqueous solutions, never in the pure state. Formula: H 2 CO 3
- A weak, unstable acid present in solutions of carbon dioxide in water. It gives carbonated beverages their sharp taste. Chemical formula: H2CO3.