keen vs lament

keen and lament both are nouns.

Word	Noun	Adjective	Verb	Adverb
keen	Yes	Yes	Yes	No
lament	Yes	No	Yes	No

As nouns, lament is a hypernym of keen; that is, lament is a word with a broader meaning than keen:

keen: a funeral lament sung with loud wailing
lament: a song or hymn of mourning composed or performed as a memorial to a dead person

Other hypernyms of keen include coronach, dirge, requiem, threnody.

As verbs, keen and lament are synonyms defined as:

keen (noun)	lament (noun)
a funeral lament sung with loud wailing	a mournful poem; a lament for the dead
	a song or hymn of mourning composed or performed as a memorial to a dead person
	a cry of sorrow and grief

keen (adjective)	lament (adjective)
excellent
intense or sharp
having or demonstrating ability to recognize or draw fine distinctions
having a sharp cutting edge or point
painful as if caused by a sharp instrument

keen (verb)	lament (verb)
express grief verbally	regret strongly
	express grief verbally