The complex radical, CO.OH, regarded as the essential and characteristic constituent which all oxygen acids of carbon (as formic, acetic, benzoic acids, etc.) have in common; -- called also oxatyl.
Refers to a functional group containing a carbon atom double bonded to an oxygen and single bonded to a hydroxyl(OH) group. Carboxyl groups are characteristic of organic acids and thus relate to the "acid" in the name amino acid.