grief vs heartache

grief and heartache both are nouns.

Word	Noun	Adjective	Verb	Adverb
grief	Yes	No	No	No
heartache	Yes	No	No	No

As nouns, grief and heartache are synonyms defined as:

grief and heartache: intense sorrow caused by loss of a loved one (especially by death)

Other synonyms of grief include brokenheartedness, heartbreak.

grief (noun)	heartache (noun)
something that causes great unhappiness	intense sorrow caused by loss of a loved one (especially by death)
intense sorrow caused by loss of a loved one (especially by death)