argument has 15 distinct synonyms spread across 6 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.
a contentious speech act; a dispute where there is strong disagreement
“they were involved in a violent argument”
a discussion in which reasons are advanced for and against some proposition or proposal
“the argument over foreign aid goes on and on”
a summary of the subject or plot of a literary work or play or movie
“the editor added the argument to the poem”
a variable in a logical or mathematical expression whose value determines the dependent variable; if f(x)=y, x is the independent variable
a course of reasoning aimed at demonstrating a truth or falsehood; the methodical process of logical reasoning
“I can't follow your line of reasoning”
Synonyms, antonyms and the broader and narrower relations for argument come from Princeton University’s WordNet. Full sources and licences.