molecule

American  

[mol-uh-kyool] / ˈmɒl əˌkjul /

noun

molecules plural

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.

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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

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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.

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molecule Cultural  

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

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Other Word Forms

Derived Forms

• submolecule
  noun
• supermolecule
  noun

Inflected Forms

Nouns

• molecules
  plural

Etymology

Origin of molecule

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

Compare meaning

How does molecule compare to similar and commonly confused words? Explore the most common comparisons:

• formula unit vs. molecule

Explanation

A molecule is the simplest structural unit of a substance that still keeps the properties of that substance, like a molecule of water. This scientific word also gets used in unscientific ways, as in "Every single molecule in my body wants that chocolate cupcake!" People sometimes confuse molecules with atoms, but a molecule is made up of atoms. A molecule retains the characteristic of the substance it’s from, so a water molecule is still water. An atom only has the characteristics of its element, not the larger composition. For example, a water molecule, H2O, is made up of two hydrogen atoms and one oxygen atom.

Example Sentences

Although creatine is best known for helping muscles rapidly regenerate adenosine triphosphate, the molecule that powers cells, the brain also depends heavily on this energy system.

From Science Daily • Jun. 30, 2026

When a lone-star tick bites you, it introduces the sugar molecule alpha-gal into your bloodstream.

From The Wall Street Journal • Jun. 25, 2026

The researchers found that OLE, a molecule derived from the PM20D1 gene, can shift microglia back into a more protective state.

From Science Daily • Jun. 19, 2026

Their research showed that probenecid alters how kidney cells handle urate, a molecule most commonly associated with gout.

From Science Daily • Jun. 17, 2026

Jessie set aside the octane gumdrop molecule she had started on and grabbed a piece of paper and a pen.

From "The Vanderbeekers of 141st Street" by Karina Yan Glaser

Related Words

• fragment
• particle