concentrate has 14 distinct synonyms spread across 7 of its 11 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 deconcentrate.
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.
make denser, stronger, or purer
“concentrate juice”
make central
“The Russian government centralized the distribution of food”
make more concise
“condense the contents of a book into a summary”
draw together or meet in one common center
“These groups concentrate in the inner cities”
the desired mineral that is left after impurities have been removed from mined ore
a concentrated form of a foodstuff; the bulk is reduced by removing water
a concentrated example of something
“the concentrate of contemporary despair”
Synonyms, antonyms and the broader and narrower relations for concentrate come from Princeton University’s WordNet. Full sources and licences.