heartache vs dolour

heartache and dolour both are nouns.

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

As nouns, dolour is a hyponym of heartache; that is, dolour is a word with a more specific, narrower meaning than heartache:

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

Other hyponyms of heartache include dolor.

heartache (noun)	dolour (noun)
intense sorrow caused by loss of a loved one (especially by death)	(poetry) painful grief