islam has 4 distinct synonyms spread across 2 of its 2 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 civilization of Muslims collectively which is governed by the Muslim religion
“Islam is predominant in northern Africa, the Middle East, Pakistan, and Indonesia”
the monotheistic religious system of Muslims founded in Arabia in the 7th century and based on the teachings of Muhammad as laid down in the Koran
“Islam is a complete way of life, not a Sunday religion”
Synonyms, antonyms and the broader and narrower relations for islam come from Princeton University’s WordNet. Full sources and licences.