colon has 3 distinct synonyms spread across 3 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. 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 part of the large intestine between the cecum and the rectum; it extracts moisture from food residues before they are excreted
the basic unit of money in El Salvador; equal to 100 centavos
the basic unit of money in Costa Rica; equal to 100 centimos
a punctuation mark (:) used after a word introducing a series or an example or an explanation (or after the salutation of a business letter)
Synonyms, antonyms and the broader and narrower relations for colon come from Princeton University’s WordNet. Full sources and licences.