knot vs unknot

knot is a noun but unknot is not a noun.

Word	Noun	Adjective	Verb	Adverb
knot	Yes	No	Yes	No
unknot	No	No	Yes	No

knot (noun)	unknot (noun)
a sandpiper that breeds in the Arctic and winters in the Southern Hemisphere
any of various fastenings formed by looping and tying a rope (or cord) upon itself or to another rope or to another object
soft lump or unevenness in a yarn; either an imperfection or created by design
a tight cluster of people or things
something twisted and tight and swollen
a hard cross-grained round piece of wood in a board where a branch emerged
(of ships and wind) a unit of speed equal to one nautical mile per hour or about 1.15 statute miles per hour

knot (verb)	unknot (verb)
tie or fasten into a knot	become or cause to become undone by separating the fibers or threads of
tangle or complicate
make into knots; make knots out of