involvement has 9 distinct synonyms spread across 4 of its 5 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 non-involvement.
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 act of sharing in the activities of a group
“the teacher tried to increase his students' engagement in class activities”
a connection of inclusion or containment
“he escaped involvement in the accident”
a sense of concern with and curiosity about someone or something
“an interest in music”
the condition of sharing in common with others (as fellows or partners etc.)
Synonyms, antonyms and the broader and narrower relations for involvement come from Princeton University’s WordNet. Full sources and licences.