ready-mix vs premix

ready-mix and premix both are nouns.

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

As nouns, premix is a hypernym of ready-mix; that is, premix is a word with a broader meaning than ready-mix:

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

Other hypernyms of ready-mix include convenience food, mix.

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