flux has 18 distinct synonyms spread across 7 of its 11 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 rate of flow of energy or particles across a given surface
a substance added to molten metals to bond with impurities that can then be readily removed
excessive discharge of liquid from a cavity or organ (as in watery diarrhea)
a state of uncertainty about what should be done (usually following some important event) preceding the establishment of a new direction of action
“the flux following the death of the emperor”
the lines of force surrounding a permanent magnet or a moving charged particle
(physics) the number of changes in energy flow across a given surface per unit area
in constant change
“his opinions are in flux”
Synonyms, antonyms and the broader and narrower relations for flux come from Princeton University’s WordNet. Full sources and licences.