unbalance vs instability

unbalance and instability both are nouns.

Word	Noun	Adjective	Verb	Adverb
unbalance	Yes	No	Yes	No
instability	Yes	No	No	No

As nouns, unbalance and instability are synonyms defined as:

Other synonyms of unbalance include imbalance.

unbalance (noun)	instability (noun)
a lack of balance or state of disequilibrium	the quality or attribute of being unstable and irresolute
a state of mental disturbance and disorientation	unreliability attributable to being unstable
	an unstable order
	a lack of balance or state of disequilibrium

unbalance (verb)	instability (verb)
derange mentally, throw out of mental balance; make insane
throw out of balance or equilibrium