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

See Examples For:

molecule molecules

The pair’s research relates to homochirality, which is the tendency of living systems to use just one of two possible mirror-image forms of a molecule.

From The Wall Street Journal ● Oct. 7, 2026

By solving the mystery of chirality, Henri Kagan and Kenso Soai worked out how to design chemical reactions to produce much more of the desired version of a molecule.

From BBC ● Oct. 7, 2026

The researchers discovered how nature exclusively makes the correct version of a molecule - rather than its mirror image.

From BBC ● Oct. 7, 2026

Previous experiments could capture individual parts of this process, but they could not provide a combined picture of both the electronic changes inside the molecule and the reorganization occurring around it.

From Science Daily ● Oct. 6, 2026

A year to eighteen months of steady work might tell something more solid about the shape of the hemoglobin molecule.

From "Double Helix" by James D. Watson

Sensing these invisible molecules is much less straightforward, yet it holds a lot of business promise—especially for a company like Moët Hennessy.

From The Wall Street Journal ● Oct. 7, 2026

And while nature almost exclusively produces the version it requires to function, chemical reactions in a lab usually create a 50/50 mix of both left- and right-handed molecules.

From BBC ● Oct. 7, 2026

The Nobel laureates answered the question: Why does life favour just one of these mirror image molecules over the other.

From BBC ● Oct. 7, 2026

"This gives us a new way to understand how molecules and their environments evolve together during fundamental chemical transformations."

From Science Daily ● Oct. 6, 2026

Zoom in even more, and you’ll see cells and the molecules they are made from.

From "Meltdown" by Deirdre Langeland

Related Words

• fragment
• particle