molecule
noun
mol·e·cule
ˈmä-li-ˌkyül 
1
: the smallest particle of a substance that retains all the properties (see property sense 1a) of the substance and is composed of one or more atoms (see atom sense 1a)
a molecule of water
a molecule of oxygen
2
: a tiny bit : particle
There is a molecule of evidence to support these charges.
Examples of molecule in a Sentence
There is not a molecule of evidence to support these charges.
not a molecule of sense in that girl
Recent Examples on the Web
These nanosheets have a very high surface area and strong catalytic properties, helping ethanol molecules react more quickly on the sensor surface.
—
Bojan Stojkovski, Interesting Engineering, 1 Feb. 2026
Oxidative stress is an imbalance between highly reactive molecules produced in cells and antioxidants (such as vitamin C).
—Julie Scott, Verywell Health, 31 Jan. 2026
Researchers first synthesized the molecule by applying an electric discharge to a substance called thiophenol — a foul-smelling liquid containing sulfur, carbon and hydrogen.
—Jacopo Prisco, CNN Money, 30 Jan. 2026
Astrocytes appear to keep track of people’s increasing sleep debt throughout the day, likely through a buildup of calcium, and secrete sleep-inducing molecules that alter brain activity.
—Ingrid Wickelgren, Quanta Magazine, 30 Jan. 2026
See All Example Sentences for molecule
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Bojan Stojkovski, Interesting Engineering, 1 Feb. 2026
Oxidative stress is an imbalance between highly reactive molecules produced in cells and antioxidants (such as vitamin C).
—Julie Scott, Verywell Health, 31 Jan. 2026
Researchers first synthesized the molecule by applying an electric discharge to a substance called thiophenol — a foul-smelling liquid containing sulfur, carbon and hydrogen.
—Jacopo Prisco, CNN Money, 30 Jan. 2026
Astrocytes appear to keep track of people’s increasing sleep debt throughout the day, likely through a buildup of calcium, and secrete sleep-inducing molecules that alter brain activity.
—Ingrid Wickelgren, Quanta Magazine, 30 Jan. 2026
See All Example Sentences for molecule
Cite this Entry
“Molecule.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/molecule. Accessed 4 Feb. 2026.
Copy CitationKids Definition
molecule
noun
mol·e·cule
ˈmäl-i-ˌkyü(ə)l
1
: the smallest particle of a substance having all the characteristics of the substance
a molecule of water
a molecule of oxygen
2
: a very small bit : particle
Medical Definition
molecule
noun
mol·e·cule
ˈmäl-i-ˌkyü(ə)l
: the smallest particle of a substance that retains all the properties of the substance and is composed of one or more atoms
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