Any person involved in a transaction or proceeding. A group of voters organized for the purpose of influencing governmental policy, particularly through the nomination and election of candidates for public office.
Plaintiffs and defendants are PARTIES in lawsuits, for example. They have the right to make claims and defenses, offer proof, and examine and cross-examine witnesses at trials. They can pursue appeals after unsatisfactory judgments if they satisfy designated criteria.
In the United States, the Democrats and the Republicans make up the two major national political parties.