phantom limb vs illusion

phantom limb and illusion both are nouns.

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

As nouns, illusion is a hypernym of phantom limb; that is, illusion is a word with a broader meaning than phantom limb:

phantom limb: the illusion that a limb still exists after it has been amputated
illusion: an erroneous mental representation

Other hypernyms of phantom limb include semblance.

phantom limb (noun)	illusion (noun)
the illusion that a limb still exists after it has been amputated	the act of deluding; deception by creating illusory ideas
	an illusory feat; considered magical by naive observers
	something many people believe that is false
	an erroneous mental representation