1keen 
/ˈki:n/ adjective
keen·er; keen·est /ˈki:n/ adjective [also more keen; most keen] 1 : having or showing an ability to think clearly and to understand what is not obvious or simple about something
▪ a keen intellect/intelligence/mind ▪ She's a very keen observer of the political world. ▪ She made some keen [=acute] observations. ▪ a keen wit 2 : very strong and sensitive : highly developed
▪ The dog has a keen sense of smell. = The dog has a keen nose. ▪ keen [=acute] eyesight/hearing ▪ She had a keen awareness of what was happening. [=she knew exactly what was happening] ▪ She has a keen ear for languages. [=she is able to easily learn and understand languages] ▪ He has a keen eye for details. [=he is good at noticing details] 3 a : very excited about and interested in something
▪ She's a keen tennis player. = She's keen about tennis. ▪ He's a keen student of art history. = He has a keen interest in art history.
b : feeling a strong and impatient desire to do something
▪ He is keen [=eager] to learn more about art history. 4 : strong or intense
▪ After his death, she felt a keen [=profound] sense of loss. ▪ The two firms are in keen competition. ▪ (chiefly Brit) a keen wind 5 informal + old-fashioned : very good : wonderful
▪ Gee, that's keen. ◊This sense is now usually used in a playful or ironic way. — see also peachy keen 6 literary : having a sharp edge or point
▪ a keen knife/sword 7 Brit, of a price : very low
▪ They sell reliable products at very keen prices.
▪ a keen intellect/intelligence/mind ▪ She's a very keen observer of the political world. ▪ She made some keen [=acute] observations. ▪ a keen wit
▪ The dog has a keen sense of smell. = The dog has a keen nose. ▪ keen [=acute] eyesight/hearing ▪ She had a keen awareness of what was happening. [=she knew exactly what was happening] ▪ She has a keen ear for languages. [=she is able to easily learn and understand languages] ▪ He has a keen eye for details. [=he is good at noticing details]
▪ She's a keen tennis player. = She's keen about tennis. ▪ He's a keen student of art history. = He has a keen interest in art history.
b : feeling a strong and impatient desire to do something
▪ He is keen [=eager] to learn more about art history.
▪ After his death, she felt a keen [=profound] sense of loss. ▪ The two firms are in keen competition. ▪ (chiefly Brit) a keen wind
▪ Gee, that's keen. ◊This sense is now usually used in a playful or ironic way. — see also peachy keen
▪ a keen knife/sword
▪ They sell reliable products at very keen prices.
(as) keen as mustard
Brit : very excited and interested : very enthusiastic
▪ I gave him the job because he was willing to learn and seemed as keen as mustard.
▪ I gave him the job because he was willing to learn and seemed as keen as mustard.
keen on 1 : very excited about and interested in (something)
▪ She's very keen on tennis. ▪ I'm not keen on that idea. [=I don't like that idea] ▪ (Brit) He's mad keen on golf. 2 chiefly Brit : interested in or attracted to (someone)
▪ He's been very keen on her since they met at my party.
▪ She's very keen on tennis. ▪ I'm not keen on that idea. [=I don't like that idea] ▪ (Brit) He's mad keen on golf.
▪ He's been very keen on her since they met at my party.
— keen·ly adverb
▪ They were keenly interested in how well I was doing. ▪ a keenly felt change ▪ The parents were keenly aware of the teacher's importance.
▪ They were keenly interested in how well I was doing. ▪ a keenly felt change ▪ The parents were keenly aware of the teacher's importance.
— keen·ness /ˈki:nnəs/ noun
[noncount] ▪ The keenness of the saw made cutting the board easier. [singular] ▪ a keenness of sight
/ˈki:nnəs/ noun [noncount] ▪ The keenness of the saw made cutting the board easier. [singular] ▪ a keenness of sight
