Plaintiff (noun)

1. A person who brings a legal action against another in a court of law.
2. A person who initiates a lawsuit or makes a formal complaint.
3. A person who brings a case against another person in a court of law.

Origin:

Late middle english: from old french plaitif, -ive, from plait "plea", based on latin placitum "something agreed upon".

Examples:

1. He was the plaintiff in the lawsuit.
2. She was the plaintiff in the case against the company.
3. The plaintiffs were seeking damages.
4. He was representing the plaintiff in court.
5. She was the plaintiff in the divorce case.