The adjective volatile means something that is likely to change suddenly and unexpectedly.

Synonyms are explosive, changeable, erratic, or fickle.

The word origins from Middle French (16th century) volatile, from Latin volatilis meaning “fleeting, transitory, swift, rapid, flying, winged”, from past participle stem of volare meaning “to fly”. Its meaning “readily changing, flighty, fickle” is first recorded in the 1640s.

If you don’t want to take more risks, choose less volatile investments.

Volatile chemicals could be dangerous.

Her volatile moods are not helpful on completing the project.