In chemistry there are two distinct theories to explain acid-base reactions; the Bronsted-Lowry and Lewis acid-base theories. The Bronsted-Lowry theory talks about removal or transfer of hydrogen ions (H+) ie. protons; where as the Lewis theory talks about donation or acceptance of electron pairs. It is important to distinguish and recognise the two as in nature acids and bases can behave either as Bronsted-Lowry or Lewis acids and bases. A Brønsted–Lowry acid is a chemical species being able to donate a hydrogen cation, H+. Obviously, it needs another chemical species (base) to accept the transferred hydrogen cation. A Lewis acid is a chemical species being able to accept an electron-pair, reacting thereby with a Lewis base to form a Lewis bond, ie. a shared electron pair between Lewis acid and base.