Other forms: proportions
A proportion is one part measured against the whole. Two students out of twenty is a small proportion of the class; a large proportion of the repair bill went on the roof.
It is also the relation of sizes inside one thing: a face drawn out of proportion, a room with fine proportions, a mixture in the proportion three to one. In the plural it can mean sheer size, especially size that has got away from you — the fire reached alarming proportions. The word lives in set phrases: in proportion to, out of all proportion, and a sense of proportion, which is the ability to judge how much something really matters. The adjectives are proportional and proportionate — a fine proportional to your income. One trap: after 'a proportion of' with a plural noun, British English takes a plural verb, so a proportion of the seats were empty.
1nounproportionA part of something, measured against the whole.
“Only a small proportion of the audience stayed to the end.”
synonyms: share, fraction, percentage
2nounrelationshipThe relationship in size or amount between two things.
“Mix the sand and cement in a proportion of three to one.”
3nounpluralIn the plural, the size or dimensions of something.
“The cathedral's proportions are hard to take in from close up.”
proportion is a measure.
Proportion came through Old French from Latin prōportiō, which meant a comparative relation, a symmetry, an analogy. Break the Latin open and you find pro, 'for' or 'before', with portio, 'a share or part' — a share held up against something else. That is still what the word does: it names a part you can only understand by looking at what it belongs to.
Latin
prōportiō — comparative relation, proportion, symmetry, analogy
Old French
proportion
Middle English
proporcion
English, today
proportion
Built from
From Middle English proporcion, from Old French proportion, from Latin prōportiō (“comparative relation, proportion, symmetry, analogy”), from pro (“for, before”) + portio (“share, part”); see portion. by surface analysis, pro- + portion.
Etymology from Wiktionary, CC BY-SA