Answer. According to Bronsted-Lowry concept, a base is a substance that can accept a proton (H+) from another substance.
For example, when HC1 dissolves in water; HC1 acts as an acid and H2O as a base because it takes proton from HC1.
HCl(aq) + H2O(aq) —————> H3O+ (aq) + Cl- (aq)
Acid Base Conjugate acid Conjugate base