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formaldehyde

American  
[fawr-mal-duh-hahyd, fer-] / fɔrˈmæl dəˌhaɪd, fər- /

noun

Chemistry.

  1. a colorless, toxic, potentially carcinogenic, water-soluble gas, CH 2 O, having a suffocating odor, usually derived from methyl alcohol by oxidation: used chiefly in aqueous solution, as a disinfectant and preservative, and in the manufacture of various resins and plastics.

formaldehyde British  
/ fɔːˈmældɪˌhaɪd /

noun

  1. Systematic name: methanal.  a colourless poisonous irritating gas with a pungent characteristic odour, made by the oxidation of methanol and used as formalin and in the manufacture of synthetic resins. Formula: HCHO

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
formaldehyde Scientific  
/ fôr-măl′də-hīd′ /

  1. A colorless gas having a sharp, suffocating odor. It is used in making plastics and, when dissolved in a solution of water and methanol, to preserve biological specimens. Chemical formula: CH 2 O.

Etymology

Origin of formaldehyde

1870–75; form(ic) + aldehyde; modeled on German Formaldehyd

Compare meaning

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Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Composite wood products can be bound with formaldehyde.

From BBC • Mar. 16, 2026

Preserved in formaldehyde and paraffin wax, they come from patients treated at the UK's national bowel hospital, St Mark's, in northwest London.

From Barron's • Feb. 4, 2026

Others include multiple types of exposures associated with fume events: chemicals that appear in both pesticides and engine oils; high levels of ultrafine particles and solvents like formaldehyde; and brain trauma.

From The Wall Street Journal • Dec. 22, 2025

In particular, they cited the government’s evaluation of chemicals including formaldehyde, inorganic arsenic and hexavalent chromium, which can be used or created by industrial processes.

From Los Angeles Times • Jul. 25, 2025

They’d been placed in formaldehyde because Zanmi Lasante didn’t have the equipment to preserve the specimens in frozen sections.

From "Mountains Beyond Mountains" by Tracy Kidder and Michael French

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.