denial vs defense mechanism

denial and defense mechanism both are nouns.

Word	Noun	Adjective	Verb	Adverb
denial	Yes	No	No	No
defense mechanism	Yes	No	No	No

As nouns, defense mechanism is a hypernym of denial; that is, defense mechanism is a word with a broader meaning than denial:

denial: (psychiatry) a defense mechanism that denies painful thoughts
defense mechanism: (psychiatry) an unconscious process that tries to reduce the anxiety associated with instinctive desires

Other hypernyms of denial include defence, defence mechanism, defence reaction, defense, defense reaction.

denial (noun)	defense mechanism (noun)
a defendant's answer or plea denying the truth of the charges against him	(psychiatry) an unconscious process that tries to reduce the anxiety associated with instinctive desires
renunciation of your own interests in favor of the interests of others
the act of refusing to comply (as with a request)
the act of asserting that something alleged is not true
(psychiatry) a defense mechanism that denies painful thoughts