willing vs happy

willing is a noun but happy is not a noun.

Word	Noun	Adjective	Verb	Adverb
willing	Yes	Yes	No	No
happy	No	Yes	No	No

willing (noun)	happy (noun)
the act of making a choice

willing (adjective)	happy (adjective)
disposed or inclined toward	enjoying or showing or marked by joy or pleasure
not brought about by coercion or force	well expressed and to the point
	marked by good fortune
	eagerly disposed to act or to be of service