The Collaborative International Dictionary of English v.0.48:
Proportional \Pro*por"tion*al\, a. [L. proportionalis: cf. F.
1. Having a due proportion, or comparative relation; being in
suitable proportion or degree; as, the parts of an edifice
are proportional. --Milton.
2. Relating to, or securing, proportion. --Hutton.
3. (Math.) Constituting a proportion; having the same, or a
constant, ratio; as, proportional quantities; momentum is
proportional to quantity of matter.
Proportional logarithms, logistic logarithms. See under
Proportional scale, a scale on which are marked parts
proportional to the logarithms of the natural numbers; a
Proportionalscales, compasses, dividers, etc.
(Draughting), instruments used in making copies of
drawings, or drawings of objects, on an enlarged or