mourning vs sorrow

mourning and sorrow both are nouns.

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

As nouns, sorrow is a hypernym of mourning; that is, sorrow is a word with a broader meaning than mourning:

Other hypernyms of mourning include sadness, sorrowfulness.

mourning (noun)	sorrow (noun)
the passionate and demonstrative activity of expressing grief	something that causes great unhappiness
state of sorrow over the death or departure of a loved one	an emotion of great sadness associated with loss or bereavement
	sadness associated with some wrong done or some disappointment
	the state of being sad

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

mourning (verb)	sorrow (verb)
	feel grief