illustration vs fig

illustration and fig both are nouns.

Word	Noun	Adjective	Verb	Adverb
illustration	Yes	No	No	No
fig	Yes	No	No	No

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

Other hyponyms of illustration include pictorial matter, picture, figure.

illustration (noun)	fig (noun)
a visual representation (a picture or diagram) that is used to make some subject more pleasing or easier to understand	a diagram or picture illustrating textual material
an item of information that is typical of a class or group	fleshy sweet pear-shaped yellowish or purple multiple fruit eaten fresh or preserved or dried
artwork that helps make something clear or attractive	Mediterranean tree widely cultivated for its edible fruit
showing by example