rectangular vs perpendicular

rectangular is not a noun while perpendicular is a noun.

Word	Noun	Adjective	Verb	Adverb
rectangular	No	Yes	No	No
perpendicular	Yes	Yes	No	No

rectangular (noun)	perpendicular (noun)
	an extremely steep face
	a cord from which a metal weight is suspended pointing directly to the earth's center of gravity; used to determine the vertical from a given point
	a Gothic style in 14th and 15th century England; characterized by vertical lines and a four-centered (Tudor) arch and fan vaulting
	a straight line at right angles to another line

rectangular (adjective)	perpendicular (adjective)
having four right angles	intersecting at or forming right angles
having a set of mutually perpendicular axes; meeting at right angles	at right angles to the plane of the horizon or a base line
	so steep as to be nearly vertical