A ketone is a carbonyl compound, containing a carbon–oxygen double bond (C=O), in which the carbonyl carbon is bonded to two other carbon atoms, written R–CO–R′. Because the carbonyl carbon carries no hydrogen, a ketone is not readily oxidised, in contrast to an aldehyde. Ketones are named with the suffix '-one'; for example, propanone (commonly called acetone) has its C=O carbon flanked by two methyl groups.

酮是一种羰基化合物,含有碳氧双键(C=O),其中羰基碳连接两个其他碳原子,写作 R–CO–R′。由于羰基碳上不带氢,酮不易被氧化,这与醛形成对照。酮以词尾“-one(酮)”命名;例如丙酮(俗称阿西酮)的 C=O 碳两侧各连一个甲基。