a change or variation occurring in the course of something.

interchange or alternation, as of states or things.

vicissitudes, successive, alternating, or changing phases or conditions, as of life or fortune; ups and downs

They remained friends through the vicissitudes of 40 years.

regular change or succession of one state or thing to another.

change; mutation; mutability.

noun

stability , stagnation

noun

about-face * , alteration , alternation , diversity , flip-flop * , fluctuation , innovation , mid-course correction , mutability , mutation , novelty , permutation , progression , reversal , revolution , shift , sport , switch , switchover , transposition , turnaround , uncertainty , ups and downs * , variation , variety , asperity , hardship , rigor , change , difficulty