Changeable, unstable, inconstant, likely to change or shift rapidly and unpredictably: The stock market is often volatile; a person may have volatile moods; the weather in New England is notoriously volatile.
→ Synonyms of volatile include fickle, flighty, capricious (kuh-PRISHus, word 11 of Level 1), erratic, protean (PROH-tee-in), and mercurial (mur-KYUR-ee-ul).
Antonyms include stable, fixed, steadfast, invariable, immutable, and quiescent (kwy-ES-int, word 22 of Level 3).
Volatile, which entered English in the early 1600s, has a volatile history, full of many shifts and changes in meaning. The word comes from the Latin volare, to fly, and its original meaning was “flying” or “having the power to fly.” Today volatile is rarely used in this sense, and instead we have the word volant (VOH-lant), which came into the language shortly before volatile from the same Latin volare, to fly. Volant means flying, able to fly, or quick, nimble, agile.
The fickle, unpredictable volatile then came to mean evaporating quickly, easily vaporized, as a volatile oil or liquid. In the science of chemistry it is still used in this way, and today it would be unusual but not outlandish for an essayist to write about the volatile morning dew, or for a weathercaster to speak of volatile fog or clouds, or for a TV chef to discuss the volatile nature of wine used in cooking.
By the mid-seventeenth century the inconstant volatile had acquired its most durable meaning: changeable, unstable, inconstant, likely to change or shift rapidly and unpredictably. In this sense it is a close synonym of capricious and mercurial. Out of this notion of changeability and inconstancy, volatile gained two more meanings: fleeting, vanishing swiftly, transient, ephemeral; and also lighthearted, lively and carefree, whimsical, prone to flights of fancy.
In the second half of the twentieth century volatile took on yet another meaning: explosive, likely to erupt into violence. You will often hear volatile used this way in news reports about domestic or international affairs characterized by tension and sporadic conflict. This sense is an outgrowth of the meaning “unstable, unpredictable,” for when a situation is unstable or unpredictable it is often likely to explode or erupt in violence.
Finally, in the 1990s volatile acquired one more sense. According to Webster’s New World Dictionary, third college edition, in the jargon of computer science volatile is used to mean pertaining to “memory that does not retain stored data when the power supply is disconnected.”
Despite its capricious, changeable history, volatile has remained close to its roots. For as I’m sure you can see, all the various senses of volatile incorporate the notions of flight, flightiness, and swift, unpredictable change suggested by the word’s Latin root, volare, to fly. When you see or hear volatile used, and when you use it yourself, remember that in all of its senses the word describes that which can swiftly fly away from one condition or mood into another.
Volatile is the adjective; the corresponding noun is volatility.
