What is the antonym for caliph?
That just doesn't make sense. You can have an antonym for an
adjective (the antonym of quick is slow), for an adverb (the
antonym of quickly is slowly), and for certain verbs (sleep/wake,
speak/shut up, etc.), certain abstract nouns (love/hate - also used
as verbs) but it simply doesn't make sense to talk about antonyms
of nouns which represent objects.