Father Christmas vs Saint Nick

Father Christmas and Saint Nick both are nouns.

Word	Noun	Adjective	Verb	Adverb
Father Christmas	Yes	No	No	No
Saint Nick	Yes	No	No	No

As nouns, Father Christmas and Saint Nick are synonyms defined as:

Father Christmas and Saint Nick: the legendary patron saint of children; an imaginary being who is thought to bring presents to children at Christmas

Other synonyms of Father Christmas include Kriss Kringle, Saint Nicholas, Santa, Santa Claus, St. Nick.

Father Christmas (noun)	Saint Nick (noun)
the legendary patron saint of children; an imaginary being who is thought to bring presents to children at Christmas	the legendary patron saint of children; an imaginary being who is thought to bring presents to children at Christmas