Santa Claus vs Father Christmas

Santa Claus and Father Christmas both are nouns.

Word	Noun	Adjective	Verb	Adverb
Santa Claus	Yes	No	No	No
Father Christmas	Yes	No	No	No

As nouns, Santa Claus and Father Christmas are synonyms defined as:

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

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

Santa Claus (noun)	Father Christmas (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