communication has 1 distinct synonym spread across 1 of its 3 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 activity of communicating; the activity of conveying information
“they could not act without official communication from Moscow”
something that is communicated by or to or between people or groups
a connection allowing access between persons or places
“how many lines of communication can there be among four people?”
Synonyms, antonyms and the broader and narrower relations for communication come from Princeton University’s WordNet. Full sources and licences.