What does aldehyde mean?
An aldehyde is an organic compound defined by the presence of a formyl group — a carbonyl carbon double-bonded to oxygen and single-bonded to hydrogen, written –CHO — attached to another atom or group. This structure makes aldehydes among the most reactive and versatile compounds in organic chemistry: they sit at a pivotal point between alcohols and carboxylic acids, since oxidizing a primary alcohol yields an aldehyde, and further oxidation converts it into an acid. Familiar examples include formaldehyde, used in resins and preservation, and acetaldehyde, an intermediate in alcohol metabolism. Aldehydes also shape everyday sensory experience, contributing characteristic aromas to vanilla, cinnamon, citrus peel, and aged wines such as sherry. The name itself derives from a contraction of 'alcohol dehydrogenatus', reflecting how the class was first identified. Although chiefly a technical term encountered in chemistry, biochemistry, perfumery, and food science, the word surfaces in public discussion wherever air quality, preservatives, or metabolic health are debated.
nounAn organic compound containing the group –CHO, formed by the oxidation of a primary alcohol and characterized by the carbonyl carbon bonded to at least one hydrogen atom. Aldehydes are reactive intermediates in many industrial processes and occur naturally in essential oils and biological systems.
- Any of a class of organic compounds containing the formyl group (–CHO), with the general formula R–CHO.
- A specific individual compound belonging to this class, such as formaldehyde or acetaldehyde.
"The winemaker detected faint notes of aldehyde in the sherry, giving it its distinctive nutty aroma."
"Formaldehyde, the simplest aldehyde, is widely used as a preservative and in resin manufacture."
"During fermentation, acetaldehyde accumulates briefly before yeast enzymes reduce it to ethanol."
Standard English pluralization; used when referring to multiple members of the aldehyde class collectively.
"Aldehydes released from new furniture and paints can contribute to indoor air pollution."
The word 'aldehyde' is literally a contraction of 'alcohol dehydrogenated' — chemists squeezed two words into one to name the compound left behind when you strip hydrogen from alcohol.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of aldehyde
The word 'aldehyde' was coined in the early nineteenth century by the German chemist Justus von Liebig, who formed it as a contraction of the New Latin phrase 'alcohol dehydrogenatus', meaning 'alcohol deprived of hydrogen'. The term entered English shortly afterward through chemical literature. It shares its root with 'alcohol', which itself traces back through Arabic 'al-kuḥl' — a fine powder originally used for eye makeup — before being adopted into European chemistry vocabulary. Related English derivatives include the adjective 'aldehydic' and the plural 'aldehydes'.
Related word forms
How aldehyde is actually used
A technical term used chiefly in chemistry, biochemistry, and related scientific fields; rare in everyday conversation. In casual speech, specific aldehydes such as formaldehyde are far more commonly referenced than the class name itself. The plural 'aldehydes' is standard when referring to multiple members of the class.
Easily confused with aldehyde
An aldehyde has its carbonyl group bonded to at least one hydrogen atom (at the end of a carbon chain), whereas a ketone's carbonyl group is bonded to two carbon atoms within the chain.
An alcohol contains a hydroxyl (–OH) group rather than the formyl (–CHO) group that defines an aldehyde; aldehydes are typically formed by oxidizing primary alcohols.