altitudinous vs altitude

altitudinous is not a noun while altitude is a noun.

Word	Noun	Adjective	Verb	Adverb
altitudinous	No	Yes	No	No
altitude	Yes	No	No	No

altitudinous (noun)	altitude (noun)
	elevation especially above sea level or above the earth's surface
	angular distance above the horizon (especially of a celestial object)
	the perpendicular distance from the base of a geometric figure to the opposite vertex (or side if parallel)

altitudinous (adjective)	altitude (adjective)
indefinitely high; lofty