molecule

IPA/ˈmɒlɪkjuːl/
KK[mˈɑləkjˌul]IPA/ˈmɑːlɪkjuːl/

molecule — noun

  • moleculesingular
  • moleculesplural

1. the tiniest piece of a chemical material that still behaves like that material,

1.nounB2
Definition

the tiniest piece of a chemical material that still behaves like that material, made when several atoms become linked by chemical bonds

Example

A water molecule has two hydrogen atoms and one oxygen atom bonded together.

pattern: a [substance] molecule + has/consists of

Selim's teacher drew a diagram showing how each salt molecule forms a repeating pattern.

pattern: each + [substance] + molecule

Common collocations
  • molecule of water / oxygen / carbon dioxide
  • DNA molecule
  • complex molecule
  • molecule contains / consists of / is made up of
Synonyms
  • compound

    a specific type of molecule made of two or more different elements joined together, whereas molecule can refer to any bonded group of atoms

Grammar Patterns

a molecule of [substance]

[substance] molecule

Usage Note

In technical chemistry, a single atom of a noble gas (such as helium) is not considered a molecule — molecules always involve two or more atoms bonded together.

Common Mistakes

A molecule of hydrogen gas is just one atom.
A molecule of hydrogen gas has two atoms joined together; a single hydrogen atom by itself is not a molecule.
Atoms are the building blocks of molecules; molecules contain two or more atoms.

2. a very small piece or amount of a substance, especially when you want to emphasi

2.nounC1
Definition

a very small piece or amount of a substance, especially when you want to emphasize that there is extremely little or none at all

Example

The technician wiped the lens until not a molecule of dust remained on the surface.

negative construction: not a molecule of [substance]

Hoa noticed tiny molecules of grease floating on the surface of the soup.

non-technical use with everyday material

Common collocations
  • molecule of dust / grease / dirt / food
Synonyms
  • particle

    a more general word for any tiny piece of matter; does not carry the chemical meaning of two or more bonded atoms

  • speck

    even smaller and more informal than molecule in this sense; typically used for visible tiny bits (e.g., a speck of dust)

  • bit

    the most everyday word; less precise but natural in conversation

Grammar Patterns

not a molecule of [substance]

a molecule of [substance/material]

Usage Note

This sense is non-technical and informal. It is different from sense 1 because it does not refer to a specific chemical structure — it simply means a very tiny bit of something. It appears often in negative statements for extra emphasis.

Common Mistakes

There is not a molecule of sugar in this drink' (said loosely about soda).
There are millions of molecules of sugar in this drink
it is very sweet.' — In everyday speech the non-technical sense is acceptable, but in precise science contexts sense 1 should be used.

Word family

  • molecular
    adjectiveB2
  • intermolecular
    adjectiveC1
  • molecularly
    adverbC1

Synonym discussion

Sense: noun/1

A molecule is the smallest unit of a chemical substance that keeps its properties, made from two or more atoms bonded together. An atom is even smaller — it is a single element's basic building block, and atoms join up to form molecules. A particle is a broader term for any tiny piece of matter; it could be a single atom, a molecule, or even a visible speck of dust. A compound is a substance formed when two or more different elements bond in fixed proportions — all compounds are made of molecules, but not all molecules are compounds (for instance, O₂ is an oxygen molecule but not a compound because both atoms are the same element). In everyday conversation, particle is the simplest choice. In chemistry class, molecule and atom are the precise terms you need.

atom ↗particle ↗compound ↗

Common collocations

Nouns

Phrases

  • a molecule of [substance]
  • not a molecule of [substance]
  • molecule consists of
  • molecule contains
  • molecule is made up of

Prepositions

Etymology

LatinFrenchEnglish

The word molecule comes from the French 'molécule', which was created in the 1600s from the Latin 'moles' meaning 'mass'. Scientists needed a word for the tiniest piece of a chemical substance that still acts like that substance, and 'molecule' filled that role. The related word 'atom' has a different history — from Greek 'atomos' meaning 'uncuttable' — and refers to the even smaller particles that join together to form molecules.