Molecular

google

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

wiktionary

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molecule +‎  -ar

etymonline

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molecular (adj.)

"relating to or consisting of molecules," by 1815, from molecule + -ar or else from French moléculaire or Modern Latin molecularis. Molecular biology is attested by 1950.