combining weight meaning

NounPLcombining weightsPREcom-
1. (chemistry, dated) The proportional weight, usually referred to hydrogen as a standard, and for each element a fixed multiple of the atomic weight, by which an element unites with another to form a distinct compound.

Meaning of combining weight for the defined word.

Grammatically, this idiom "combining weight" is a noun, more specifically, a countable noun.

Definiteness: Level 1

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Definite ➨ Versatile