Definition

1. Noun:
   • (Non-technical usage) A tiny piece of anything: A very small particle or amount of a substance.
   • (Physics and Chemistry) The simplest structural unit of an element or compound: The smallest particle of a substance that retains all the chemical properties of that substance. It is composed of two or more atoms held together by chemical bonds.

Examples of Usage

• Non-technical usage:

  • There wasn't a molecule of truth in his story. (His story was completely false.)
  • A molecule of dust floated in the sunbeam. (A tiny speck of dust was visible.)

• Physics and Chemistry usage:

  • A water molecule consists of two hydrogen atoms and one oxygen atom. (H₂O is the chemical formula for water.)
  • Oxygen gas in the air exists as a diatomic molecule, O₂. (Two oxygen atoms are bonded together.)

Advanced Usage

• "Polar molecule": A molecule in which the distribution of electrons between the atoms is uneven, creating a positive end and a negative end.
  • Water is a polar molecule, which is why it is such a good solvent.
• "Molecular structure": The specific arrangement of atoms within a molecule.
  • The drug's effectiveness depends on its complex molecular structure.

Variants and Related Words

• Molecular (adj): Relating to or consisting of molecules.
  • The scientist studied the molecular weight of the compound.
• Diatomic molecule (n): A molecule composed of only two atoms.
  • Nitrogen gas (N₂) is a common diatomic molecule.

Synonyms

• Particle: A minute portion of matter.
• Speck: A tiny spot or particle.

Related Phrases

• "Not a molecule of [something]": An idiom used for emphasis to mean "not even the smallest amount."
  • He didn't show a molecule of remorse for his actions. (He showed no remorse at all.)

Noun

1. (nontechnical usage) a tiny piece of anything
2. (physics and chemistry) the simplest structural unit of an element or compound