case in point vs illustration

case in point and illustration both are nouns.

Word	Noun	Adjective	Verb	Adverb
case in point	Yes	No	No	No
illustration	Yes	No	No	No

As nouns, illustration is a hypernym of case in point; that is, illustration is a word with a broader meaning than case in point:

case in point: an example that is used to justify similar occurrences at a later time
illustration: an item of information that is typical of a class or group

Other hypernyms of case in point include example, instance, representative.

case in point (noun)	illustration (noun)
an example that is used to justify similar occurrences at a later time	a visual representation (a picture or diagram) that is used to make some subject more pleasing or easier to understand
	an item of information that is typical of a class or group
	artwork that helps make something clear or attractive
	showing by example