emphasis If you say that someone is mad keen on something, you are emphasizing that they are very enthusiastic about it. So you're not mad keen on science then?. to sing a loud, sad song for someone who has died
very penetrating and clear and sharp in operation; "an incisive mind"; "a keen intelligence"; "of sharp and active intellect"
You use keen to indicate that someone has a lot of enthusiasm for a particular activity and spends a lot of time doing it. She was a keen amateur photographer
Sharp; having a fine edge or point; as, a keen razor, or a razor with a keen edge
Acute of mind; sharp; penetrating; having or expressing mental acuteness; as, a man of keen understanding; a keen look; keen features
as physically painful as if caused by a sharp instrument; "a cutting wind"; "keen winds"; "knifelike cold"; "piercing knifelike pains"; "piercing cold"; "piercing criticism"; "a stabbing pain"; "lancinating pain"