Brønsted base

A molecular entity capable of accepting a hydron (proton) from an acid (i.e. a 'hydron acceptor') or the corresponding chemical species. For example: OH, H2O, CH3CO2, HSO4, SO42−, Cl .
See also: conjugate acid-base pair
PAC, 1994, 66, 1077 (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1091