What is the synonym of word Keen which an adjective?

Here are some synonyms for "keen" as an adjective, depending on the specific meaning you want to convey:

For "eager" or "enthusiastic":

* Eager

* Ardent

* Enthusiastic

* Passionate

* Zealous

* Fervent

* Intense

* Excited

* Animated

* Buoyant

For "sharp" or "intense":

* Sharp

* Acute

* Piercing

* Intense

* Strong

* Powerful

* Vigorous

* Cutting

* Poignant

* Biting

For "clever" or "intelligent":

* Sharp

* Astute

* Intelligent

* Bright

* Smart

* Perceptive

* Insightful

* Shrewd

* Clever

* Witty

For "interested" or "attentive":

* Interested

* Attentive

* Curious

* Observant

* Alert

* Aware

* Sensitive

* Responsive

The best synonym for "keen" will depend on the context of its use.