Remembrance Sunday vs Remembrance Day

Remembrance Sunday and Remembrance Day both are nouns.

Word	Noun	Adjective	Verb	Adverb
Remembrance Sunday	Yes	No	No	No
Remembrance Day	Yes	No	No	No

As nouns, Remembrance Sunday and Remembrance Day are synonyms defined as:

Remembrance Sunday and Remembrance Day: the Sunday nearest to November 11 when those who died in World War I and World War II are commemorated

Other synonyms of Remembrance Sunday include Poppy Day.

Remembrance Sunday (noun)	Remembrance Day (noun)
the Sunday nearest to November 11 when those who died in World War I and World War II are commemorated	the Sunday nearest to November 11 when those who died in World War I and World War II are commemorated