O. Henry vs William Sydney Porter

O. Henry and William Sydney Porter both are nouns.

Word	Noun	Adjective	Verb	Adverb
O. Henry	Yes	No	No	No
William Sydney Porter	Yes	No	No	No

As nouns, O. Henry and William Sydney Porter are synonyms defined as:

O. Henry and William Sydney Porter: United States writer of short stories whose pen name was O. Henry (1862-1910)

Other synonyms of O. Henry include Porter.

O. Henry (noun)	William Sydney Porter (noun)
United States writer of short stories whose pen name was O. Henry (1862-1910)	United States writer of short stories whose pen name was O. Henry (1862-1910)