The carboxyl group is the functional group of carboxylic acids, –COOH, which combines a carbonyl group (C=O) and a hydroxyl group (–OH) on the same carbon. It matters because the interaction between these two parts gives the group its acidity: loss of the hydroxyl proton produces a resonance-stabilised anion. The name 'carboxyl' itself reflects this combination of carbonyl and hydroxyl.

羧基是羧酸的官能团 –COOH,它在同一碳上同时结合了羰基(C=O)和羟基(–OH)。它之所以重要,是因为这两部分之间的相互作用赋予该基团酸性:失去羟基质子会生成一个因共振而稳定的阴离子。“carboxyl(羧基)”这个名称本身正反映了羰基(carbonyl)与羟基(hydroxyl)的这种结合。