proportion has 5 distinct synonyms spread across 4 of its 7 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is disproportion.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the quotient obtained when the magnitude of a part is divided by the magnitude of the whole
the relation between things (or parts of things) with respect to their comparative quantity, magnitude, or degree
“an inordinate proportion of the book is given over to quotations”
harmonious arrangement or relation of parts or elements within a whole (as in a design)
“in all perfectly beautiful objects there is found the opposition of one part to another and a reciprocal balance”
give pleasant proportions to
“harmonize a building with those surrounding it”
adjust in size relative to other things
Synonyms, antonyms and the broader and narrower relations for proportion come from Princeton University’s WordNet. Full sources and licences.