The term for a molecule that can donate a proton in a chemical reaction is an acid. According to the Brønsted-Lowry theory, an acid is defined as a proton donor, while a base is a proton acceptor. Acids play a significant role in chemical reactions, influencing pH levels, reactivity, and the behavior of different substances in solution. Common examples include hydrochloric acid (HCl) and sulfuric acid (H₂SO₄), each exhibiting unique properties and uses.