Compounds RC(=O)H , in which a carbonyl group is bonded to one hydrogen atom and to one R group.
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1312 [Terms] [Paper]
See also:
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2173 [Terms] [Paper]