Rules on Civil Procedure
Section 1. Who may be parties; plaintiff and defendant. - Only natural or juridical persons, or entities authorized by law may be parties in a civil action. The term "plaintiff" may refer to the claiming party, the counter-claimant, the cross-claimant, or the third (fourth, etc.) - party plaintiff. The term "defendant" may refer to the original defending party, the defendant in a counter-claim, the cross-defendant, or the third (fourth, etc.) - party defendant. (1a)