delusion vs illusion

delusion and illusion both are nouns.

Word	Noun	Adjective	Verb	Adverb
delusion	Yes	No	No	No
illusion	Yes	No	No	No

As nouns, delusion and illusion are synonyms defined as:

delusion and illusion: the act of deluding; deception by creating illusory ideas

Other synonyms of delusion include head game.

delusion (noun)	illusion (noun)
the act of deluding; deception by creating illusory ideas	the act of deluding; deception by creating illusory ideas
a mistaken or unfounded opinion or idea	an illusory feat; considered magical by naive observers
(psychology) an erroneous belief that is held in the face of evidence to the contrary	something many people believe that is false
	an erroneous mental representation