Duke of Wellington vs Wellington

Duke of Wellington and Wellington both are nouns.

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

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

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

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

Duke of Wellington (noun)	Wellington (noun)
British general and statesman; he defeated Napoleon at Waterloo; subsequently served as Prime Minister (1769-1852)	(19th century) a man's high tasseled boot
	the capital of New Zealand
	British general and statesman; he defeated Napoleon at Waterloo; subsequently served as Prime Minister (1769-1852)