The Brønsted-Lowry Theory is a fundamental concept in chemistry that defines acids and bases based on their ability to donate or accept protons (H⁺ ions). According to this theory, an acid is any substance that can donate a proton, while a base is any substance that can accept a proton. This approach broadens the understanding of acid-base reactions beyond just the presence of hydroxide ions. This theory is particularly useful in explaining reactions in various solvents, not just water. For example, in a reaction between hydrochloric acid (HCl) and ammonia (NH₃), HCl donates a proton to NH₃, making HCl the acid and NH₃ the base. This framework helps chemists predict the behavior of substances in different chemical environments.