adjective

keen

KEEN/kiːn/

Sharply penetrating in its effect.

The knife’s keen edge cuts the tomato into paper-thin slices.

A keen kitchen knife with an exceptionally fine edge, shown partway through a ripe tomato beside several paper-thin, intact slices.

Etymology

keenOld Englishbold, brave; clever, wise

Old English cene combined ideas of bravery and skill. English developed senses of eagerness and physical sharpness, with sharpness extending to biting cold and shrill sounds; the earliest underlying meaning remains somewhat obscure.

In context

Eloise Zinck11:39

A cheetah's eyesight is keen, and in good daylight, she can spot prey over 3 miles away.

Fawn identity [Impala and Gazelle Documentary] | Wild Things

More examples

A keen wind cuts through my thin jacket.
Her keen hearing picks up the faintest sounds.
He feels keen disappointment when the trip is canceled.
She takes a keen interest in local history.

Forms

keen · keener · keenest

keenly adverb — With sharp perception or strong feeling.

keenness noun — Sharpness, intensity, or eagerness of feeling.

Similar words

sharp: Broader term for cutting edges, acute senses, or intensity.
piercing: Emphasizes an effect that seems to penetrate forcefully.
acute: Often describes highly sensitive perception or intense pain.