Labile

labile  \LAY-byle\  adjective

: readily or frequently changing: as

a: readily or continually undergoing chemical, physical, or biological change or breakdown

b: characterized by wide fluctuations (as in blood pressure)

c: emotionally unstable

 Usage:
The researcher spent years studying chemically labile compounds in the hopes that they could be adapted into new medications.
 
“Pat takes this to heart. He develops ‘game plans’ for how he will handle conflicts and setbacks. And he applies them to his burgeoning relationship with an emotionally labile young woman who recruits him to train for a dance competition with her.” — From a movie review by Christen Giblin in the Sentinel-Tribune (Ohio), April 25, 2013

We are confident that you won’t slip up or err in learning today’s word, despite its etymology. “Labile” was borrowed into English from French and can be traced back (by way of Middle French “labile,” meaning “prone to err”) to the Latin verb “labi,” meaning “to slip or fall.” Indeed, the first sense of “labile” in English was “prone to slip, err, or lapse,” but that usage is now obsolete. Other “labi” descendants in English include “collapse,” “elapse,” “prolapse,” and simply “lapse.”

Entry in Webster's Dictionary

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