Law of definite proportions Meaning, Definition & Usage

  1. noun (chemistry) law stating that every pure substance always contains the same elements combined in the same proportions by weight
    law of constant proportion.

WordNet

Definitions
  1. (Chem.), the essential law of chemical combination that every definite compound always contains the same elements in the same proportions by weight; and, if two or more elements form more than one compound with each other, the relative proportions of each are fixed. Compare Law of multiple proportions, under Multiple.

Webster 1913