Definition
Very interested in something, or eager to do it. Can also mean sharp, quick, or highly developed (as in a keen eye or keen mind).
Example
She has a keen interest in learning new languages.
Show translation
She has a very strong, eager interest in learning new languages.
Etymology
From Old English *cēne*, meaning bold or brave, related to Old Norse *kœnn* (skilled, wise) and German *kühn* (daring). Over time the meaning shifted in English from "bold" to "sharp" and then "eager" — the sense of a sharp mind cutting keenly through a problem bridged the two ideas.
Cultural note
In British English, *keen* is an especially common way to say "enthusiastic" or "eager" — "Are you keen?" is a perfectly natural question. In American English, the "eager/enthusiastic" sense is understood but less frequent in everyday speech; Americans more often say "excited about" or "into." Keen also appears in the set phrase *keen as mustard* (British informal: extremely enthusiastic). Note the separate meaning "sharp" is universal: a *keen blade*, a *keen sense of smell*.