span has 17 distinct synonyms spread across 4 of its 7 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 complete duration of something
“the job was finished in the span of an hour”
the distance or interval between two points
a unit of length based on the width of the expanded human hand (usually taken as 9 inches)
a structure that allows people or vehicles to cross an obstacle such as a river or canal or railway etc.
Synonyms, antonyms and the broader and narrower relations for span come from Princeton University’s WordNet. Full sources and licences.