concatenation has 1 distinct synonym spread across 1 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. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
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 linked together as in a chain; union in a linked series
the linking together of a consecutive series of symbols or events or ideas etc
“it was caused by an improbable concatenation of circumstances”
a series of things depending on each other as if linked together
“the chain of command”
the act of linking together as in a series or chain
Synonyms, antonyms and the broader and narrower relations for concatenation come from Princeton University’s WordNet. Full sources and licences.