Definition of molecule
1
: the smallest particle of a substance that retains all the properties (see property sense 1a) of the substance and is composed of one or more atoms (see atom sense 1a)
a molecule of water a molecule of oxygen
2
: a tiny bit : particle
a molecule of political honesty — Time
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Merriam-Webster unabridged
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Time Traveler for molecule
The first known use of molecule was in 1701
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