A species that can either donate or accept a proton is described as:

1. Some species can play either role depending on their partner. 2. Species capable of either donating or accepting protons are called amphiprotic. 3. More generally they are called amphoteric, a term used for acids and bases under other definitions too. 4. Bicarbonate is the standard example, reacting as an acid with water in one equation and as a base in another. _Source: OpenStax Chemistry 2e (CC BY 4.0), Ch 14 'Acid-Base Equilibria', sections 14.1-14.7_