- Today's Word
Immutable
ih-MYOO-tuh-buhl
Definition
- (adjective) Unchanging over time or unable to be changed.
Example
The laws of physics are often regarded as immutable, governing the universe with unwavering consistency.
Fun Fact
“Immutable” comes from the Latin immutabilis, combining in- (“not”) and mutabilis (“changeable”). The word has been used to describe enduring principles, truths, or conditions. Its philosophical roots remind us of humanity’s quest to understand what is permanent in an ever-changing world.
(adjective) Deliberately untrustworthy and deceitful; guilty of betraying trust or breaking faith.
The perfidious advisor had been leaking confidential strategy to competitors for years, all while accepting promotions and praise from the company he was quietly destroying.
Perfidious derives from the Latin perfidiosus, meaning “treacherous,” rooted in perfidia — “faithlessness” — built from per- (“through” or “away”) and fides (“faith” or “trust”). The same root fides gives us fidelity, confide, and fiduciary — making perfidious the dark twin of an entire family of words built on trust and loyalty. It entered English in the 16th century and has carried its sense of calculated, deliberate betrayal ever since.