Philippopolis vs Plovdiv

Philippopolis and Plovdiv both are nouns.

Word	Noun	Adjective	Verb	Adverb
Philippopolis	Yes	No	No	No
Plovdiv	Yes	No	No	No

As nouns, Philippopolis and Plovdiv are synonyms defined as:

Philippopolis and Plovdiv: an ancient city in southern Bulgaria; commercial center of an agricultural region

Philippopolis (noun)	Plovdiv (noun)
an ancient city in southern Bulgaria; commercial center of an agricultural region	an ancient city in southern Bulgaria; commercial center of an agricultural region