What is the Latin word for proportion?

The usual Latin words for “proportion” are prōportiō, commētior, symmetria; also analogia, similitūdō, ineō. The right choice depends on the sense; see the distinctions below.

English → Latin

“proportion” in Latin

prōportiōproportion; symmetry; analogy commētiorto measure; to measure or compare with or by; proportion symmetriasymmetry, proportion analogiaanalogy, similarity; ratio, proportion similitūdōLikeness, resemblance, similarity; imitation.; A comparison, simile, similitude; analogy; parable.; Sameness, uniformity ineōto enter, go into; to begin; to have sexual intercourse

The English word proportion itself goes back to Latin portiō, through prōportiō.

Riddle & Arnold A Copious and Critical English–Latin Lexicon, 1864

proportion

Comparative relation, proportio (explained by Vitr., 3, 1, 1, est ratae partis membrorum in omni opere totiusque commodulatio): commensus (the proper quantity determined by measurement: also, with genitive, proportionis; Vid: Vitr. 3, 1, 2): symmetria (the whole whose parts are in proportion, Vitr. 1, 2, 4, ex ipsius operis membris conveniens consensus ex partibusque separatis ad universae figurae speciem ratae partis responsus; and 8, 1, 3, expressed by circumlocution; ad universam totius magnitudinis ex partibus singulis convenientissimus commensuum responsus. Pliny says the Latin language has no corresponding word, 34, 8, 19, no. 6, §65): congruentia aequalitasque (correspondence and equality of parts, with reference to the whole; Vid: Plin., Ep., 2, 5, 11). The proportion (symmetry) of anybody’s figure, limbs, convenientia partium; apta membrorum compositio; membrorum omnium competentia (Gell.); membrorum aequitas et commoditas (Suet., Oct., 79, of the body): his other limbs were without exception, in the exactest proportion (i. e., to the breadth of his shoulders), ceteris quoque membris usque ad imos pedes fuit aequalis et congruens (Suet., Tiberius, 68, init.): in proportion, proportione; aequaliter; congruenter: built in proportion, proportione constructus (of a body): in perfect proportion, omnibus membris usque ad imos pedes aequalis et congruens (of a person; Suet., Tiberius, 68, init.): to be (to be made, etc.) in proportion, inter se cum quodam lepore consentire; suos habere commensus proportionis; proportionibus ad summam figurationem corporis respondere (of the members of the body; Vid: Cic., Off., 1, 28, 98; Vit., 3, 1, 2 and 4): in proportion to, ad (with accusative of thing): pro: pro rata parte. Sometimes by ut est, etc. In proportion to the times, ut tum erant tempora.

Fixed part, rata pars.

Analogy, analogia: proportio (Varr. and Cic.): similitudo (likeness).

proportion v.

*justa ratione describere: pro rata parte ratione distinguere (Cic., Rep., 6, 18): well proportioned, proportione constructus (of bodies): perfectly well proportioned, omnibus membris usque ad imos pedes aequalis et congruens (after Suet., Tib., 68, init; of a man): to be well proportioned [Vid: “to be made in PROPORTION”]. To be beautifully proportioned in all its details, ad universam totius magnitudinis summam ex partibus singulis convenientissimum habere commensuum responsum (of the details, etc., of a temple, Vitr. 3, 1, 3).

Quick answer

What is the Latin word for proportion?: The usual Latin words for “proportion” are prōportiō, commētior, symmetria; also analogia, similitūdō, ineō. The right choice depends on the sense; see the distinctions below.

Entry from J. E. Riddle & T. K. Arnold, A Copious and Critical English–Latin Lexicon (rev. C. Anthon, New York: Harper, 1864), digitised by Fergus J. P. Walsh, CC BY-SA 4.0; Latin markup adapted by latindictionary.co.