What is the definition of a base according to Bronsted-Lowry theory?

According to the Bronsted-Lowry theory, a base is defined as a proton acceptor. This theory focuses on the transfer of protons (H⁺ ions) in chemical reactions, establishing an acid-base relationship. In this context, when a base encounters a proton, it accepts it, forming a conjugate acid in the process. This definition is pivotal because it broadens the understanding of acid-base chemistry beyond just the presence of hydroxide ions or the typical Arrhenius definition, which classifies acids and bases based on their behavior in water.

Understanding this concept allows chemists to identify bases even in reactions that do not involve water directly. For instance, ammonia (NH₃) can accept a proton to form ammonium (NH₄⁺), demonstrating its role as a Bronsted-Lowry base. This versatility in the definition showcases the broader applicability of the Bronsted-Lowry theory in various chemical reactions.