unbuttoned vs unfastened

unbuttoned and unfastened both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unbuttoned	No	Yes	No	No
unfastened	No	Yes	No	No

As adjectives, unbuttoned and unfastened are synonyms defined as:

unbuttoned (adjective)	unfastened (adjective)
not buttoned	not closed or secured
not under constraint in action or expression	not buttoned
	not tied
	affording unobstructed entrance and exit; not shut or closed