St. Christopher vs Christopher

St. Christopher and Christopher both are nouns.

Word	Noun	Adjective	Verb	Adverb
St. Christopher	Yes	No	No	No
Christopher	Yes	No	No	No

As nouns, St. Christopher and Christopher are synonyms defined as:

St. Christopher and Christopher: Christian martyr and patron saint of travellers (3rd century)

Other synonyms of St. Christopher include Saint Christopher.

St. Christopher (noun)	Christopher (noun)
the largest of the islands comprising Saint Christopher-Nevis	Christian martyr and patron saint of travellers (3rd century)
Christian martyr and patron saint of travellers (3rd century)