illusion vs phantom

illusion and phantom both are nouns.

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

As nouns, phantom is a hyponym of illusion; that is, phantom is a word with a more specific, narrower meaning than illusion:

Other hyponyms of illusion include apparition, fantasm, phantasm, phantasma, shadow, irradiation, phantom limb.

illusion (noun)	phantom (noun)
the act of deluding; deception by creating illusory ideas	something existing in perception only
an illusory feat; considered magical by naive observers	a ghostly appearing figure
something many people believe that is false
an erroneous mental representation

illusion (adjective)	phantom (adjective)
	something apparently sensed but having no physical reality