imbalance vs instability

imbalance and instability both are nouns.

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

As nouns, imbalance and instability are synonyms defined as:

Other synonyms of imbalance include unbalance.

imbalance (noun)	instability (noun)
lack of proportion; imbalance among the parts of something	the quality or attribute of being unstable and irresolute
a lack of balance or state of disequilibrium	unreliability attributable to being unstable
	an unstable order
	a lack of balance or state of disequilibrium