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

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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

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Compare meaning

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

• formula unit vs. molecule

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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

Sunlight is absorbed by chlorophyll, a large, complex molecule found in microscopic bodies called chloroplasts, which give plants their green color.

From The Wall Street Journal ● Oct. 16, 2026

This helped preserve the favorable interactions instead of allowing the molecule to flex and lose energy.

From Science Daily ● Oct. 8, 2026

The process begins when a section of DNA is copied into messenger RNA, a molecule that carries genetic instructions to the cell's protein-producing machinery.

From Science Daily ● Oct. 8, 2026

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

From BBC ● Oct. 7, 2026

Interrupting her harangue, I asserted that the simplest form for any regular polymeric molecule was a helix.

From "Double Helix" by James D. Watson

Carbon dioxide and water meet in the chloroplasts, where solar energy breaks down their molecules and reassembles them into the sugar glucose plus “a side order of oxygen,” the author writes.

From The Wall Street Journal ● Oct. 16, 2026

Specialized immune receptors can recognize these foreign molecules and trigger a protective response.

From Science Daily ● Oct. 15, 2026

In the study, published in Science Advances, researchers examined precisely how HMA domains interact with the molecules released by the blast fungus.

From Science Daily ● Oct. 15, 2026

Other potential uses include manipulating microscopic particles, cells, and molecules with light, as well as developing more resilient quantum systems.

From Science Daily ● Oct. 13, 2026

The obscuring lanes of dust contain organic molecules; some of them contain stars in the earliest stages of formation.

From "Cosmos" by Carl Sagan

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Related Words

• fragment
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