St. Mark vs Saint Mark

St. Mark and Saint Mark both are nouns.

Word	Noun	Adjective	Verb	Adverb
St. Mark	Yes	No	No	No
Saint Mark	Yes	No	No	No

As nouns, St. Mark and Saint Mark are synonyms defined as:

St. Mark and Saint Mark: Apostle and companion of Saint Peter; assumed to be the author of the second Gospel

Other synonyms of St. Mark include Mark, Mark the Evangelist.

St. Mark (noun)	Saint Mark (noun)
Apostle and companion of Saint Peter; assumed to be the author of the second Gospel	Apostle and companion of Saint Peter; assumed to be the author of the second Gospel