instability vs unbalance

instability and unbalance both are nouns.

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

As nouns, instability and unbalance are synonyms defined as:

Other synonyms of instability include imbalance.

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

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