Captain John Smith vs John Smith

Captain John Smith and John Smith both are nouns.

Word	Noun	Adjective	Verb	Adverb
Captain John Smith	Yes	No	No	No
John Smith	Yes	No	No	No

As nouns, Captain John Smith and John Smith are synonyms defined as:

Captain John Smith and John Smith: English explorer who helped found the colony at Jamestown, Virginia; was said to have been saved by Pocahontas (1580-1631)

Other synonyms of Captain John Smith include Smith.

Captain John Smith (noun)	John Smith (noun)
English explorer who helped found the colony at Jamestown, Virginia; was said to have been saved by Pocahontas (1580-1631)	English explorer who helped found the colony at Jamestown, Virginia; was said to have been saved by Pocahontas (1580-1631)