chain vs unchain

chain is a noun but unchain is not a noun.

Word	Noun	Adjective	Verb	Adverb
chain	Yes	No	Yes	No
unchain	No	No	Yes	No

chain (noun)	unchain (noun)
a series of (usually metal) rings or links fitted into one another to make a flexible ligament
a necklace made by stringing objects together
anything that acts as a restraint
a linked or connected series of objects
a series of things depending on each other as if linked together
(business) a number of similar establishments (stores or restaurants or banks or hotels or theaters) under one ownership
(chemistry) a series of linked atoms (generally in an organic molecule)
a series of hills or mountains
a unit of length

chain (verb)	unchain (verb)
fasten or secure with chains	remove the chains from
connect or arrange into a chain by linking	make free