unsubstantial vs immaterial

unsubstantial and immaterial both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unsubstantial	No	Yes	No	No
immaterial	No	Yes	No	No

unsubstantial (adjective)	immaterial (adjective)
lacking material form or substance; unreal	not consisting of matter
	of no importance or relevance especially to a law case
	without material form or substance
	not pertinent to the matter under consideration
	(often followed by `to') lacking importance; not mattering one way or the other