William Gilbert vs Sir William Gilbert

William Gilbert and Sir William Gilbert both are nouns.

Word	Noun	Adjective	Verb	Adverb
William Gilbert	Yes	No	No	No
Sir William Gilbert	Yes	No	No	No

As nouns, William Gilbert and Sir William Gilbert are synonyms defined as:

William Gilbert and Sir William 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, W. S. Gilbert, William S. Gilbert, William Schwenk Gilbert.

William Gilbert (noun)	Sir William 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)