common has 12 distinct synonyms spread across 7 of its 10 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 2 recorded opposites are individual, uncommon.
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.
belonging to or participated in by a community as a whole; public
“for the common good”
having no special distinction or quality; widely known or commonly encountered; average or ordinary or usual
“the common man”
being or characteristic of or appropriate to everyday language
“common parlance”
a piece of open land for recreational use in an urban area
“they went for a walk in the park”
1 of the 10 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for common.
Synonyms, antonyms and the broader and narrower relations for common come from Princeton University’s WordNet. Full sources and licences.