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

a molecule of political honesty

—Time

Synonyms

• particle
• speck
• atom
• bit
• fleck
• patch
• grain
• snippet
• scrap
• granule
• mouthful
• crumb

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

From this distance, Swift detected the faint ultraviolet glow of hydroxyl (OH), the product of water molecules broken apart by sunlight, the study reports. —Sharmila Kuthunur, Space.com, 10 Oct. 2025

The new smart insulin combines both insulin and glucagon into one molecule. —Hannah Millington, MSNBC Newsweek, 10 Oct. 2025

In fact, pTau217 is a tau molecule that has undergone phosphorylation at a position that scientists call 217. —Robert Martone, Scientific American, 10 Oct. 2025

These external influences excite the molecules and atoms in the rings, creating ions. —Big Think, 9 Oct. 2025

Word History

Etymology

French molécule, from New Latin molecula, diminutive of Latin moles mass

First Known Use

1701, in the meaning defined at sense 1

Rhymes for molecule

• minuscule
• overrule
• poiseuille
• reticule
• ridicule
• vestibule
• ampoule
• bascule
• carpool
• cesspool
• ferrule
• footstool

Kids 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