Troy vs Ilium

Troy and Ilium both are nouns.

Word	Noun	Adjective	Verb	Adverb
Troy	Yes	No	No	No
Ilium	Yes	No	No	No

As nouns, Troy and Ilium are synonyms defined as:

Troy and Ilium: an ancient city in Asia Minor that was the site of the Trojan War

Other synonyms of Troy include Ilion.

Troy (noun)	Ilium (noun)
an ancient city in Asia Minor that was the site of the Trojan War	an ancient city in Asia Minor that was the site of the Trojan War