bereaved vs mourning

bereaved and mourning both are nouns.

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

As adjectives, bereaved and mourning are synonyms defined as:

Other synonyms of bereaved include bereft, grief-stricken, grieving, sorrowing.

bereaved (noun)	mourning (noun)
a person who has suffered the death of someone they loved	the passionate and demonstrative activity of expressing grief
	state of sorrow over the death or departure of a loved one

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