名詞 lament:

1. a cry of sorrow and grief
   同義詞：lamentation, plaint, wail
2. a song or hymn of mourning composed or performed as a memorial to a dead person
   同義詞：dirge, coronach, requiem, threnody
3. a mournful poem; a lament for the dead
   同義詞：elegy

動詞 lament:

1. express grief verbally
   同義詞：keen
2. regret strongly
   同義詞：deplore, bewail, bemoan

1. A poem or song composed especially as a lament for a deceased person.
   挽歌，挽詩專門為悼念某一死者所寫的詩或歌
2. Short pleasure, long lament.
   [諺]痛快一時，痛苦一世。
3. He deeply lamented the death of his wife.
   他對妻子的去世深感悲痛。

la.ment

v.（動詞）
la.ment.ed,la.ment.ing,la.ments
v.tr.（及物動詞）
To express grief for or about; mourn:
悲痛：向…或為…表述哀痛；哀悼：
例句：
lament a death.
為死者哀悼

To regret deeply; deplore:
非常懊悔；痛惜：
例句：
He lamented his thoughtless acts.
他非常懊悔自己輕率的舉動

v.intr.（不及物動詞）
To grieve audibly; wail.
痛哭失聲；嚎啕
To express sorrow or regret.See Synonyms at grieve
表達悲傷或懊悔參見 grieve
n.（名詞）
A feeling or an expression of grief; a lamentation.
悲痛的情感或表達；悲傷
A song or poem expressing deep grief or mourning.
挽歌：表達深切的悲傷或哀悼的歌或詩

來源：
Middle English lementen
中古英語 lementen
from Old French lamenter
源自 古法語 lamenter
from Latin l3ment3ro
源自 拉丁語 l3ment3ro
from l3mentum [lament]
源自 l3mentum [哀悼]

【引伸】
lament.er
n.（名詞）