First Duke of Wellington vs Duke of Wellington

First Duke of Wellington and Duke of Wellington both are nouns.

Word	Noun	Adjective	Verb	Adverb
First Duke of Wellington	Yes	No	No	No
Duke of Wellington	Yes	No	No	No

As nouns, First Duke of Wellington and Duke of Wellington are synonyms defined as:

First Duke of Wellington and Duke of Wellington: British general and statesman; he defeated Napoleon at Waterloo; subsequently served as Prime Minister (1769-1852)

Other synonyms of First Duke of Wellington include Arthur Wellesley, Iron Duke, Wellington.

First Duke of Wellington (noun)	Duke of Wellington (noun)
British general and statesman; he defeated Napoleon at Waterloo; subsequently served as Prime Minister (1769-1852)	British general and statesman; he defeated Napoleon at Waterloo; subsequently served as Prime Minister (1769-1852)