rudiment vs rudimentary

rudiment is a noun but rudimentary is not a noun.

Word	Noun	Adjective	Verb	Adverb
rudiment	Yes	No	No	No
rudimentary	No	Yes	No	No

rudiment (noun)	rudimentary (noun)
the remains of a body part that was functional at an earlier stage of life

rudiment (adjective)	rudimentary (adjective)
	being or involving basic facts or principles
	being in the earliest stages of development
	not fully developed in mature animals