premix vs ready-mix

premix and ready-mix both are nouns.

Word	Noun	Adjective	Verb	Adverb
premix	Yes	No	No	No
ready-mix	Yes	No	No	No

As nouns, ready-mix is a hyponym of premix; that is, ready-mix is a word with a more specific, narrower meaning than premix:

premix: a commercially prepared mixture of dry ingredients
ready-mix: a commercial preparation containing most of the ingredients for a dish

Other hyponyms of premix include self-raising flour, self-rising flour.

premix (noun)	ready-mix (noun)
a commercially prepared mixture of dry ingredients	a commercial preparation containing most of the ingredients for a dish