Demetrius vs Demetrius Poliorcetes

Demetrius and Demetrius Poliorcetes both are nouns.

Word	Noun	Adjective	Verb	Adverb
Demetrius	Yes	No	No	No
Demetrius Poliorcetes	Yes	No	No	No

As nouns, Demetrius and Demetrius Poliorcetes are synonyms defined as:

Demetrius and Demetrius Poliorcetes: son of Antigonus Cyclops and king of Macedonia; he and his father were defeated at the battle of Ipsus (337-283 BC)

Other synonyms of Demetrius include Demetrius I, Demetrius I of Macedon.

Demetrius (noun)	Demetrius Poliorcetes (noun)
son of Antigonus Cyclops and king of Macedonia; he and his father were defeated at the battle of Ipsus (337-283 BC)	son of Antigonus Cyclops and king of Macedonia; he and his father were defeated at the battle of Ipsus (337-283 BC)