mourning vs lamentation

mourning and lamentation both are nouns.

Word	Noun	Adjective	Verb	Adverb
mourning	Yes	Yes	No	No
lamentation	Yes	No	No	No

As nouns, mourning and lamentation are synonyms defined as:

mourning and lamentation: the passionate and demonstrative activity of expressing grief

mourning (noun)	lamentation (noun)
the passionate and demonstrative activity of expressing grief	the passionate and demonstrative activity of expressing grief
state of sorrow over the death or departure of a loved one	a cry of sorrow and grief

mourning (adjective)	lamentation (adjective)
sorrowful through loss or deprivation