Thessaloniki vs Salonika

Thessaloniki and Salonika both are nouns.

Word	Noun	Adjective	Verb	Adverb
Thessaloniki	Yes	No	No	No
Salonika	Yes	No	No	No

As nouns, Thessaloniki and Salonika are synonyms defined as:

Thessaloniki and Salonika: a port city in northeastern Greece on an inlet of the Aegean Sea; second largest city of Greece

Other synonyms of Thessaloniki include Salonica, Thessalonica.

Thessaloniki (noun)	Salonika (noun)
a port city in northeastern Greece on an inlet of the Aegean Sea; second largest city of Greece	a port city in northeastern Greece on an inlet of the Aegean Sea; second largest city of Greece