A Lewis base is a chemical species that donates an electron pair to form a covalent bond with a Lewis acid. This concept is part of the broader Lewis theory of acids and bases, which focuses on electron pair interactions rather than proton transfer. Lewis bases can be neutral molecules or negatively charged ions. Common examples of Lewis bases include ammonia (NH₃) and water (H₂O), both of which have lone pairs of electrons available for bonding. In chemical reactions, the ability of a Lewis base to donate electrons plays a crucial role in the formation of new compounds.