The Brønsted-Lowry theory defines acids and bases based on their ability to donate or accept protons (H⁺ ions). According to this theory, an acid is a substance that donates a proton, while a base is one that accepts a proton. This framework helps explain acid-base reactions in various chemical contexts. In a Brønsted-Lowry reaction, the acid and base interact to form a conjugate base and a conjugate acid, respectively. This concept is essential for understanding many chemical processes, including those in biological systems and industrial applications. The theory broadens the scope of acid-base chemistry beyond just Arrhenius definitions.