mercurial
Mercurial describes someone whose mood or temperament changes rapidly, unpredictably, and often quite suddenly. The term is derived from the god Mercury, who was known for his swiftness and cunning, painting a mental image of a person who is as flighty and quicksilver as liquid metal. While it can be used to describe inanimate things like the weather or stock markets, it is most commonly applied to human personalities. It carries a slightly sophisticated, literary tone and usually implies a sense of instability or volatility that can make it difficult to know what to expect from someone or something.
In conversation
Discussing a coworker
I never know how to approach Mark lately.
I never know how to approach Mark lately.
Yeah, he’s become quite mercurial since the project started.
Yeah, he’s become quite mercurial since the project started.
Used to describe a person whose behavior is hard to predict.
Watching a film
That character's shift from joy to rage was intense.
That character's shift from joy to rage was intense.
True, the writing really captured her mercurial nature.
True, the writing really captured her mercurial nature.
Used to describe a character trait in fiction.
Examples
The weather in the mountains is mercurial.
The weather in the mountains is mercurial.
Her mercurial temperament made her a challenging partner to work with.
Her mercurial temperament made her a challenging partner to work with.
Despite his mercurial genius, the artist struggled to maintain consistent relationships with his patrons.
Despite his mercurial genius, the artist struggled to maintain consistent relationships with his patrons.
