open up vs unfasten

open up and unfasten both are verbs.

Word	Noun	Adjective	Verb	Adverb
open up	No	No	Yes	No
unfasten	No	No	Yes	No

As verbs, unfasten is a hyponym of open up; that is, unfasten is a word with a more specific, narrower meaning than open up:

Other hyponyms of open up include fly open.

open up (verb)	unfasten (verb)
make available	become undone or untied
become available	cause to become undone
talk freely and without inhibition
cause to open or to become open
become open
open up an area or prepare a way
start to operate or function or cause to start operating or functioning