Polska vs Republic of Poland

Polska and Republic of Poland both are nouns.

Word	Noun	Adjective	Verb	Adverb
Polska	Yes	No	No	No
Republic of Poland	Yes	No	No	No

As nouns, Polska and Republic of Poland are synonyms defined as:

Polska and Republic of Poland: a republic in central Europe; the invasion of Poland by Germany in 1939 started World War II

Other synonyms of Polska include Poland.

Polska (noun)	Republic of Poland (noun)
a republic in central Europe; the invasion of Poland by Germany in 1939 started World War II	a republic in central Europe; the invasion of Poland by Germany in 1939 started World War II