Definition of molecule in English:



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

    • ‘In the water molecule there are three atoms: two of hydrogen and one of oxygen.’
    • ‘At the root of sunburn are damaging molecules, free radicals that increase when the skin gets too much sun.’
    • ‘This electricity splits the water molecules in an electrolyte, producing hydrogen.’
    • ‘It works by affecting a molecule called nitric oxide, which expands blood vessels.’
    • ‘The reactant ions have enough energy to ionise the molecules of interest but not enough to break them up.’
    particle, bit, little bit, tiny bit, tiny piece, fragment, fraction, grain, granule, crumb, morsel, mite, mote, speck, spot, dot
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Late 18th century: from French molécule, from modern Latin molecula, diminutive of Latin moles ‘mass’.