diagram vs diagrammatical

diagram is a noun but diagrammatical is not a noun.

Word	Noun	Adjective	Verb	Adverb
diagram	Yes	No	Yes	No
diagrammatical	No	Yes	No	No

diagram (noun)	diagrammatical (noun)
a drawing intended to explain how something works; a drawing showing the relation between the parts

diagram (adjective)	diagrammatical (adjective)
	shown or represented by diagrams

diagram (verb)	diagrammatical (verb)
make a schematic or technical drawing that shows interactions among variables or how something is constructed