Proportional

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late Middle English: from late Latin proportionalis, from proportio(n- ) (see proportion).

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proportional (adj.)

late 14c. proporcional (implied in proporcionalli), "having a particular correspondence, according to or having a due proportion," from Old French proporcionel and directly from Late Latin proportionalis "pertaining to proportions," from proportio "comparative relation, analogy" (see proportion (n.)). The phrase proportional representation in the political sense for representation based on numerical proportion (rather than regional division) is attested by 1821. Related: Proportionally.