molecular weight

noun

: the average mass of a molecule of a compound compared to 1/12 the mass of carbon 12 and calculated as the sum of the atomic weights of the constituent atoms

Examples of molecular weight in a Sentence

Recent Examples on the Web

That’s thanks in part to the combination of humectants (hyaluronic acid, in five molecular weights, and polyglutamic acid) and moisture-sealing lipids (murumuru butter and ceramides). —Deanna Pai, Vogue, 27 Nov. 2025

That’s thanks to the five molecular weights of hyaluronic acid inside this 2024 Best of Beauty Award winner, which hydrate on multiple levels instead of just sitting on top of skin like a basic lotion. —Christa Joanna Lee, Allure, 9 Nov. 2025

The new wetsuits that worked best were made of strong and light fiber that is often used to make sailing rope and ultra-high molecular weight polyethylene. —Laura Baisas, Popular Science, 24 Sep. 2025

Lowering the molecular weight made the compound easier for the body to absorb and interact with, while increasing the number of sulfate groups enhanced the molecule's ability to influence gut bacteria. —New Atlas, 24 Aug. 2025

Word History

First Known Use

1860, in the meaning defined above

Rhymes for molecular weight

• borosilicate
• decontaminate
• deoxycholate
• deteriorate
• differentiate
• diisocyanate
• dinoflagellate
• excommunicate
• incapacitate
• insubordinate
• intercorporate
• interpenetrate

Kids Definition

molecular weight

noun

: the weight of a molecule equal to the sum of the weights of the atoms contained in it

Medical Definition

molecular weight

noun

: the mass of a molecule that may be calculated as the sum of the atomic weights of its constituent atoms