Definition of molecule in US English:

molecule

noun

Chemistry
  • A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.

    • ‘At the root of sunburn are damaging molecules, free radicals that increase when the skin gets too much sun.’
    • ‘It works by affecting a molecule called nitric oxide, which expands blood vessels.’
    • ‘In the water molecule there are three atoms: two of hydrogen and one of oxygen.’
    • ‘The reactant ions have enough energy to ionise the molecules of interest but not enough to break them up.’
    • ‘This electricity splits the water molecules in an electrolyte, producing hydrogen.’
    particle, bit, little bit, tiny bit, tiny piece, fragment, fraction, grain, granule, crumb, morsel, mite, mote, speck, spot, dot
    View synonyms

Origin

Late 18th century: from French molécule, from modern Latin molecula, diminutive of Latin moles ‘mass’.

Pronunciation

molecule

/ˈmäləˌkyo͞ol//ˈmɑləˌkjul/