molecule
Americannoun
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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.
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Chemistry. a quantity of a substance, the weight of which, measured in any chosen unit, is numerically equal to the molecular weight; gram molecule.
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any very small particle.
noun
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the simplest unit of a chemical compound that can exist, consisting of two or more atoms held together by chemical bonds
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a very small particle
Other Word Forms
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:
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.
Vocabulary lists containing molecule
Word Generation Science - Introductory Chemistry Concepts
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Words to Know Before You Defrost the Bird
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Cell Biology - Middle School
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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.
A few weeks ago, the BBC found Molecule listings on a popular Russian online marketplace.
From BBC • Nov. 1, 2025
The layoffs follow the discontinuation of its Pharmaceutical Sciences Small Molecule operations at the site, the company said.
From Reuters • Nov. 14, 2023
We had another one about water called "H2O: The Molecule That Made Us" and a couple of feature docs as well.
From Salon • Sep. 14, 2023
In her first book, “A Molecule Away From Madness,” the neurologist Sara Manning Peskin describes what happened next.
From New York Times • Feb. 10, 2022
Molecule by molecule the rock is removed and the mineral of the concretion substituted in its place.
From The Elements of Geology by Norton, William Harmon
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.
