illusion vs delusion

illusion and delusion both are nouns.

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

As nouns, illusion and delusion are synonyms defined as:

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

Other synonyms of illusion include head game.

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