Use
In solvents other than water, acid is defined as a substance that ionizes to release the positive ion of the solvent. The Lowry-Bronsted definition of an acid as a substance that can give up a proton is useful in the understanding of a base. The most significant contribution to the theory of acids was the electron-pair concept enunciated by G. N. Lewis. According to Lewis, any molecule or ion that can combine with another molecule by forming a covalent bond with two electrons from the second molecule or ion is an acid.