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molecule

American  
[mol-uh-kyool] / ˈmɒl əˌkyul /

noun

  1. Chemistry, Physics. the smallest physical unit of an element or compound, consisting of one or more like atoms in an element and two or more different atoms in a compound.

  2. Chemistry. a quantity of a substance, the weight of which, measured in any chosen unit, is numerically equal to the molecular weight; gram molecule.

  3. any very small particle.

molecule British  
/ ˈmɒlɪˌkjuːl /

noun

  1. the simplest unit of a chemical compound that can exist, consisting of two or more atoms held together by chemical bonds

  2. a very small particle

"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
molecule Scientific  
/ mŏl′ĭ-kyo̅o̅l′ /

  1. A group of two or more atoms linked together by sharing electrons in a chemical bond. Molecules are the fundamental components of chemical compounds and are the smallest part of a compound that can participate in a chemical reaction.

molecule Cultural  

  1. A combination of two or more atoms held together by a force between them. (See covalent bond and ionic bond.)

Other Word Forms

  • submolecule noun
  • supermolecule noun

Etymology

Origin of molecule

First recorded in 1785–95; earlier molecula, from New Latin, from Latin mōlē(s) “mass” ( molar 2 ( def. ) ) + -cula -cule 1

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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.

This marks the first time this molecule has been clearly linked to how the disease develops and progresses.

From Science Daily • Mar. 24, 2026

"In Alzheimer's mice treated with the molecule, disease progression was markedly slowed," states Dr. Jing Yan, formerly part of Prof. Bading's team and now with FundaMental Pharma.

From Science Daily • Mar. 23, 2026

"We don't want side effects arising from poor-quality medicines and giving the molecule itself a bad name."

From BBC • Mar. 17, 2026

On Friday the patent on semaglutide - the molecule behind Danish drugmaker Novo Nordisk's blockbuster weight-loss drugs Wegovy and Ozempic - expires in the country.

From BBC • Mar. 17, 2026

Even more important, these hydrogen bonds were present at very low DNA concentrations, strongly hinting that the bonds linked together bases in the same molecule.

From "Double Helix" by James D. Watson

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.