series has 2 distinct synonyms spread across 2 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 serialized set of programs
“a comedy series”
(sports) several contests played successively by the same teams
“the visiting team swept the series”
(electronics) connection of components in such a manner that current flows first through one and then through the other
“the voltage divider consisted of a series of fixed resistors”
a group of postage stamps having a common theme or a group of coins or currency selected as a group for study or collection
“the Post Office issued a series commemorating famous American entertainers”
(mathematics) the sum of a finite or infinite sequence of expressions
Synonyms, antonyms and the broader and narrower relations for series come from Princeton University’s WordNet. Full sources and licences.