convenience has 14 distinct synonyms spread across 2 of its 4 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 inconvenience.
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 state of being suitable or opportune
“chairs arranged for his own convenience”
the quality of being useful and convenient
“they offered the convenience of an installment plan”
Synonyms, antonyms and the broader and narrower relations for convenience come from Princeton University’s WordNet. Full sources and licences.