alphabetic has 1 distinct synonym 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. Its one recorded opposite is analphabetic.
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.
relating to or expressed by a writing system that uses an alphabet
“alphabetical writing system”
arranged in order according to the alphabet
“an alphabetic arrangement”
Synonyms, antonyms and the broader and narrower relations for alphabetic come from Princeton University’s WordNet. Full sources and licences.