solidness vs substantial

solidness is a noun but substantial is not a noun.

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

solidness (noun)	substantial (noun)
the quality of being substantial or having substance
the quality of being solid and reliable financially or factually or morally
the consistency of a solid
the state in which a substance has no tendency to flow under moderate stress; resists forces (such as compression) that tend to deform it; and retains a definite size and shape

solidness (adjective)	substantial (adjective)
	having substance or capable of being treated as fact; not imaginary
	of considerable importance, size, or worth
	of or relating to the real nature or essential elements of something
	having an abundant supply of money or possessions of value
	of good quality and condition; solidly built
	providing abundant nourishment