chemist vs Sir Alexander Robertus Todd

chemist and Sir Alexander Robertus Todd both are nouns.

Word	Noun	Adjective	Verb	Adverb
chemist	Yes	No	No	No
Sir Alexander Robertus Todd	Yes	No	No	No

chemist (noun)	Sir Alexander Robertus Todd (noun)
a scientist who specializes in chemistry	Scottish chemist noted for his research into the structure of nucleic acids (born in 1907)
a health professional trained in the art of preparing and dispensing drugs