injection vs introduction

injection and introduction both are nouns.

Word	Noun	Adjective	Verb	Adverb
injection	Yes	No	No	No
introduction	Yes	No	No	No

As nouns, introduction is a hypernym of injection; that is, introduction is a word with a broader meaning than injection:

Other hypernyms of injection include insertion, intromission.

injection (noun)	introduction (noun)
the forceful insertion of a substance under pressure	the act of putting one thing into another
the act of putting a liquid into the body by means of a syringe	the act of beginning something new
any solution that is injected (as into the skin)	the act of starting something for the first time; introducing something new
	the first section of a communication
	formally making a person known to another or to the public
	a basic or elementary instructional text
	a new proposal