inflexible vs adamant

inflexible is not a noun while adamant is a noun.

Word	Noun	Adjective	Verb	Adverb
inflexible	No	Yes	No	No
adamant	Yes	Yes	No	No

inflexible (noun)	adamant (noun)
	very hard native crystalline carbon valued as a gem

inflexible (adjective)	adamant (adjective)
resistant to being bent	impervious to pleas, persuasion, requests, reason
incapable of change
not making concessions
incapable of adapting or changing to meet circumstances