William Gilbert vs William S. Gilbert

William Gilbert and William S. Gilbert both are nouns.

Word	Noun	Adjective	Verb	Adverb
William Gilbert	Yes	No	No	No
William S. Gilbert	Yes	No	No	No

As nouns, William Gilbert and William S. Gilbert are synonyms defined as:

William Gilbert and William S. Gilbert: a librettist who was a collaborator with Sir Arthur Sullivan in a famous series of comic operettas (1836-1911)

Other synonyms of William Gilbert include Gilbert, Sir William Gilbert, W. S. Gilbert, William Schwenk Gilbert.

William Gilbert (noun)	William S. Gilbert (noun)
English court physician noted for his studies of terrestrial magnetism (1540-1603)	a librettist who was a collaborator with Sir Arthur Sullivan in a famous series of comic operettas (1836-1911)
a librettist who was a collaborator with Sir Arthur Sullivan in a famous series of comic operettas (1836-1911)