Definition:

A plaintiff is the person bringing a civil lawsuit to court.

In a criminal case, it might be said that the plaintiff is the state, that is, the local, state, federal, or special authority who brings the case to court on behalf of the people.

Most business litigation deals with civil law; that is, one party bringing a lawsuit against another party. A "party" in these cases can be an individual or a business.

in most cases, the plaintiff has the "burden of proof;" that is, the plaintiff is required to prove his or her case is true. That makes sense, because the plaintiff is the party bringing the suit to court, so he or she should have to prove why the suit should be heard. 

A special case: In most federal tax issues, the  IRS is the plaintiff and the individual or business taxpayer is the defendant. But in the case of Tax Court, the individual taxpayer is the plaintiff and the IRS is the defendant. 

The other party in a lawsuit is the defendant, the person being sued. 

Also Known As: In an arbitration case, the person bringing the case before an arbitrator is the claimanant.

Common Misspellings: plaintive (not the same word)

Examples: The plaintiff's attorney set out the case against the defendant at the beginning of the trial.