connectedness has 3 distinct synonyms spread across 2 of its 2 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 disconnectedness, unconnectedness.
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 connected
“the connection between church and state is inescapable”
a relation between things or events (as in the case of one causing the other or sharing features with it)
“there was a connection between eating that pickle and having that nightmare”
Synonyms, antonyms and the broader and narrower relations for connectedness come from Princeton University’s WordNet. Full sources and licences.