noun
political party
A formal term for a political party, often used in legal or official contexts.
公党の代表が記者会見を開いた。
The political party's representative held a press conference.
彼は新しい公党を結成した。
He formed a new political party.
政党 is the common, everyday word for 'political party'. 公党 is more formal and often used in legal or official documents.
Compound of 公 (public) and 党 (party). The exact historical derivation is uncertain, but the spelling is conventionally associated with the meaning 'political party'.