What Is a Plaintiff in a Lawsuit?

Plaintiff in a Lawsuit Explained

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The plaintiff is the person who brings a lawsuit to court. In civil law cases, the plaintiff is also sometimes referred to as the claimant—that is, the person bringing a claim against another person.

The other party in a civil lawsuit is the defendant or respondent (the one who responds to the suit). The defendant is the person being sued or the person against whom the complaint is filed.

Learn more about how a plaintiff files a lawsuit and their role in a civil court case.


The terms "plaintiff" and "defendant" go back to medieval times when English common law practices came into being. The term "plaintiff" comes from the Old French for "aggrieved," and it has the same Latin root as "complaint." 

What Is a Plaintiff in a Lawsuit?

Most business litigation deals with civil law—that is, one party bringing a lawsuit against another party (a plaintiff bringing a suit against a defendant). A "party" in these cases can be an individual, a business, or an organization.

Civil law has mostly to do with the failure of one party to do something or avoid doing something that causes harm to another person. For instance, if one party (the defendant) fails to pay money owed to another party (the plaintiff), the plaintiff may go to court to get a verdict that the defendant must give them the amount owed.


In official court documents, the plaintiff is listed before the defendant. If the case is appealed to a higher court, the party that made the appeal to reverse the lower court's decision (the appellant) is listed before the party that is seeking to uphold the decision (the appellee).

How Does a Plaintiff File a Lawsuit?

To begin a lawsuit, the plaintiff must file a complaint and a summons in the appropriate court. These are two separate documents.

  • The complaint sets up the reasons for the lawsuit by describing what the defendant did wrong (breach of contract, for example).
  • The summons includes a copy of the complaint and sets specific requirements for the other party to respond. Sometimes the response is in written form, while at other times the summons is to appear in court (in small claims court, for example).

A defendant or their attorney has 21 days after the day they received the summons to serve on the plaintiff or their attorney a reply to the summons. The defendant must also file the response with the court. Failure to respond will result in a judgment by default against them.

The complaint, summons, defendant's response (which might include a countersuit), and other documents setting out the case are referred to as "pleadings." The lawsuit proceeds from these documents.


At any point in the process, the litigants (plaintiff and defendant) can agree to use arbitration or mediation to reach a settlement.

The Burden of Proof for the Plaintiff in Civil Lawsuits

The plaintiff has the burden of proof to prove their case is true. That makes sense because the plaintiff is the party that brought the suit to court, so they should have to prove why it should be heard and why their claim has validity. 

In civil cases, the burden of proof standard is usually preponderance of evidence. The preponderance of evidence refers to the weight of the evidence, not the amount. Under the preponderance standard, the plaintiff convinces the judge or jury that there is a greater than 50% chance that the claim is true.


Criminal cases have a higher standard: The case against the defendant—made by a prosecutor—must be proven beyond a reasonable doubt.

Tax Cases

Most federal income tax disputes are between the IRS and the individual (or business) taxpayer. If a tax case goes to a U.S. Tax Court, the individual taxpayer is the plaintiff and the IRS is the defendant. That's because the taxpayer is disputing the IRS ruling.

A Tax Court case begins with the filing of a petition by the taxpayer. Disputes involving $50,000 or less may be conducted under the court's simplified small tax case procedure. The decision in a small tax case may not be appealed by either the plaintiff or the IRS. 

Key Takeaways

  • The plaintiff, AKA as the claimant, is the person who brings a lawsuit to court.
  • The other party in a civil lawsuit is the defendant or respondent.
  • Civil law typically deals with the failure of one party to do something or avoid doing something that causes harm to another person.
  • To initiate a lawsuit, the plaintiff files both a complaint and a summons in the appropriate court.
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The Balance uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. United States Courts. "Summons in a Civil Action." Accessed Dec. 2, 2020.

  2. Cornell Legal Information Institute. "Preponderance of the Evidence." Accessed Dec. 2, 2020.

  3. U.S. Tax Court. "Information About Filing a Case in the United States Tax Court," Page 1. Accessed Dec. 2, 2020.

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