ferdinand i has 1 distinct synonym spread across 1 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.
Holy Roman Emperor and king of Hungary and Bohemia (1503-1564)
king of Castile and Leon who achieved control of the Moorish kings of Saragossa and Seville and Toledo (1016-1065)
Synonyms, antonyms and the broader and narrower relations for ferdinand i come from Princeton University’s WordNet. Full sources and licences.