hornbook vs primer

hornbook and primer both are nouns.

Word	Noun	Adjective	Verb	Adverb
hornbook	Yes	No	No	No
primer	Yes	No	No	No

As nouns, primer is a hypernym of hornbook; that is, primer is a word with a broader meaning than hornbook:

hornbook: a primer that provides instruction in the rudiments or basic skills of a branch of knowledge
primer: an introductory textbook

hornbook (noun)	primer (noun)
a primer that provides instruction in the rudiments or basic skills of a branch of knowledge	any igniter that is used to initiate the burning of a propellant
	the first or preliminary coat of paint or size applied to a surface
	an introductory textbook