injection vs insertion

injection and insertion both are nouns.

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

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

Other hypernyms of injection include introduction, intromission.

injection (noun)	insertion (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	a message (spoken or written) that is introduced or inserted
any solution that is injected (as into the skin)