poem vs lament

poem and lament both are nouns.

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

As nouns, lament is a hyponym of poem; that is, lament is a word with a more specific, narrower meaning than poem:

poem (noun)	lament (noun)
a composition written in metrical feet forming rhythmical lines	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

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