What is another word for proportionately?

It depends which proportionately you mean. In the sense “to a proportionate degree”, the synonyms are proportionally. Across all 3 senses there are 2 distinct synonyms, and they are not interchangeable with each other — this page lists them under the sense each one belongs to.

What is the opposite of proportionately?

The recorded antonym is disproportionately. Opposites are sense-specific too: this page shows which meaning each one is the opposite of, because a word rarely has a single opposite that holds for all of its senses.

Why are the synonyms for proportionately split into groups?

Because proportionately carries 3 recorded senses and each has its own set of substitutes. A single flat list would put words from unrelated meanings side by side with nothing to tell them apart, which is exactly how a writer picks the wrong one. The grouping comes from WordNet's synsets, not from an editorial judgement of ours.

Where do the synonyms for proportionately come from?

From Princeton University's WordNet, a lexical database maintained by lexicographers since 1985. A synonym here means a word form that shares a synset with this word — a set of forms interchangeable in one recorded context. Nothing on this page is generated by a language model.

Synonyms and antonyms

proportionately

proportionately/pɹəˈpɔɹʃənətli/

adverbRare

proportionately has 2 distinct synonyms spread across 2 of its 3 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 disproportionately.

2
Distinct synonyms: 1
Antonym: 3 of 3
Senses with a relation

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.