breastwork vs fortification

breastwork and fortification both are nouns.

Word	Noun	Adjective	Verb	Adverb
breastwork	Yes	No	No	No
fortification	Yes	No	No	No

As nouns, fortification is a hypernym of breastwork; that is, fortification is a word with a broader meaning than breastwork:

breastwork: fortification consisting of a low wall
fortification: defensive structure consisting of walls or mounds built around a stronghold to strengthen it

Other hypernyms of breastwork include munition.

breastwork (noun)	fortification (noun)
fortification consisting of a low wall	the addition of an ingredient for the purpose of enrichment (as the addition of alcohol to wine or the addition of vitamins to food)
	defensive structure consisting of walls or mounds built around a stronghold to strengthen it
	the art or science of strengthening defenses