D-day vs Normandy landings

D-day and Normandy landings both are nouns.

Word	Noun	Adjective	Verb	Adverb
D-day	Yes	No	No	No
Normandy landings	Yes	No	No	No

As nouns, D-day and Normandy landings are synonyms defined as:

D-day and Normandy landings: date of the Allied landing in France, World War II

Other synonyms of D-day include 6 June 1944.

D-day (noun)	Normandy landings (noun)
date of the Allied landing in France, World War II	date of the Allied landing in France, World War II