Petrograd vs Leningrad

Petrograd and Leningrad both are nouns.

Word	Noun	Adjective	Verb	Adverb
Petrograd	Yes	No	No	No
Leningrad	Yes	No	No	No

As nouns, Petrograd and Leningrad are synonyms defined as:

Petrograd and Leningrad: a city in the European part of Russia; 2nd largest Russian city; located at the head of the Gulf of Finland; former capital of Russia

Other synonyms of Petrograd include Peterburg, Saint Petersburg, St. Petersburg.

Petrograd (noun)	Leningrad (noun)
a city in the European part of Russia; 2nd largest Russian city; located at the head of the Gulf of Finland; former capital of Russia	a city in the European part of Russia; 2nd largest Russian city; located at the head of the Gulf of Finland; former capital of Russia