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.

---

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

---

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.

---

molecule Cultural  

1. A combination of two or more atoms held together by a force between them. (See covalent bond and ionic bond.)

---

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

They then select mutations unique to the patient’s cancer to incorporate into an mRNA molecule, which provides the genetic code instructing cells to produce proteins with those mutations.

From The Wall Street Journal ● Aug. 19, 2026

Hyaluronic acid is a naturally occurring sugar molecule in the body and is known as a "moisture magnet" as it grabs hold of water.

From BBC ● Aug. 15, 2026

These humble vessels of the God molecule live underground for up to nine months a year, during which time they neither eat nor move.

From The Wall Street Journal ● Aug. 11, 2026

The intron RNA survived because it forms a circular molecule with no open ends.

From Science Daily ● Aug. 5, 2026

Decisions had to be made about the number of polynucleotide chains within the DNA molecule.

From "Double Helix" by James D. Watson

The team then used metabolomic analysis to search for molecules that might be carrying this signal.

From Science Daily ● Aug. 21, 2026

For decades, scientists generally assumed that fossilization destroyed the original organic molecules once present in bones, teeth, and other tissues.

From Science Daily ● Aug. 14, 2026

Those patterns can reveal the chemical composition of distant objects and allow researchers to identify molecules and minerals on their surfaces.

From Science Daily ● Aug. 14, 2026

Mass spectrometry is a method that helps scientists identify molecules by measuring their mass and chemical properties.

From Science Daily ● Aug. 14, 2026

The string disturbs the air molecules around it as it vibrates, producing sound waves in the air.

From "Understanding Basic Music Theory" by Catherine Schmidt-Jones and Russel Jones

Related Words

• fragment
• particle