unthinkable

UK: ʌnˈθɪŋkəbl̩ | US: ʌnˈθɪŋkəbl̩

Definition

  1. adj. impossible to imagine or believe

  2. adj. contrary to what is reasonable or expected

Structure
un <not>think <consider>able <capable of>
Etymology

The word "unthinkable" combines three morphemes:

  1. "Un-" (Old English "un-"), a prefix meaning "not," negates the root.
  2. "Think" (Old English "þencan"), meaning "to consider" or "to conceive in the mind."
  3. "-able" (Latin "-abilis" via Old French), a suffix indicating capability.
    Originally, "thinkable" (early 17th century) meant "capable of being thought," but the addition of "un-" shifted the meaning to "beyond consideration" or "too improbable to conceive." The term gained prominence in the 20th century, often used in contexts like nuclear warfare ("the unthinkable scenario").
Examples

  1. The idea of total extinction seemed unthinkable to the ancient philosophers.

  2. She found it unthinkable to betray her closest friend.

  3. In the 1950s, space travel was considered unthinkable by many.

  4. The proposal was dismissed as unthinkable by the committee.

  5. Climate change has made extreme weather events once deemed unthinkable a reality.