law of definite proportions
A fundamental chemical principle stating that a given compound always contains its constituent elements in fixed mass ratios. Used in scientific contexts.
The law of definite proportions is one of the fundamental laws of chemistry.
The law of multiple proportions, which deals with elements combining in different ratios to form different compounds, whereas 定比例の法則 refers to the fixed ratio within a single compound.
A compound of 定比例 (definite proportion) + の (possessive particle) + 法則 (law). The term is a direct translation of the English 'law of definite proportions'.