button vs unbutton

button is a noun but unbutton is not a noun.

Word	Noun	Adjective	Verb	Adverb
button	Yes	No	Yes	No
unbutton	No	No	Yes	No

button (noun)	unbutton (noun)
a round fastener sewn to shirts and coats etc to fit through buttonholes
an electrical switch operated by pressing
a device that when pressed will release part of a mechanism
any artifact that resembles a button
a specific area or icon in graphical user interface systems that is clicked or pressed in order to select a command or perform an action
a female sexual organ homologous to the penis
a round flat badge displaying information and suitable for pinning onto a garment
any of various plant parts that resemble buttons

button (verb)	unbutton (verb)
fasten with buttons	undo the buttons of
provide with buttons