essential vs substantial

essential is a noun but substantial is not a noun.

Word	Noun	Adjective	Verb	Adverb
essential	Yes	Yes	No	No
substantial	No	Yes	No	No

essential (noun)	substantial (noun)
anything indispensable

essential (adjective)	substantial (adjective)
basic and fundamental	having substance or capable of being treated as fact; not imaginary
defining rights and duties as opposed to giving the rules by which rights and duties are established	of considerable importance, size, or worth
being or relating to or containing the essence of a plant etc	of or relating to the real nature or essential elements of something
of the greatest importance	having an abundant supply of money or possessions of value
absolutely necessary; vitally necessary	of good quality and condition; solidly built
	providing abundant nourishment