hallucination vs delusion

hallucination and delusion both are nouns.

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

As nouns, hallucination and delusion are synonyms defined as:

As nouns, delusion is a hypernym of hallucination; that is, delusion is a word with a broader meaning than hallucination:

hallucination: illusory perception; a common symptom of severe mental disorder
delusion: (psychology) an erroneous belief that is held in the face of evidence to the contrary

Other hypernyms of hallucination include psychotic belief.

hallucination (noun)	delusion (noun)
a mistaken or unfounded opinion or idea	the act of deluding; deception by creating illusory ideas
an object perceived during a hallucinatory episode	a mistaken or unfounded opinion or idea
illusory perception; a common symptom of severe mental disorder	(psychology) an erroneous belief that is held in the face of evidence to the contrary