The language of US litigation is rife with designations of different parties based on their role in the case. The following is a non-exhaustive list of the most important designations to know:

The familiar players

Plaintiff: The person or entity that initiates a civil lawsuit. In a criminal case, the State or the People of the State are generally designated as "Plaintiff".

Defendant: The person or entity that is sued.

Petitioner: A party filing a petition in a court. For example, the spouse filing for divorce might be referred to as the "Petitioner" in some states. This also refers to parties initiating certain appellate proceedings, e.g. petition for certiorari or petition for review.

Respondent: The party against whom the petition is filed.

Appellant: The party initiating an appeal of the decision of a lower court. Sometimes designated more precisely


Appellee: The party defending the decision of the lower court on appeal.


The hyphenations are important because the caption is not always reversed on appeal. For example, if Ron Davis sues Emiliano Schwarzenegger, the case will be Davis v. Schwarzenegger both in the trial court and on appeal. Thus, the only way to know for sure whether it's the plaintiff or defendant who's taking the appeal is to have the parties designated accordingly, e.g.





The hyphenations make clear that Davis sued Schwarzenegger, Schwarzenegger lost, and now appeals.

On petition for certiorari, the caption may or may not be reversed, depending on who filed the petition. If the plaintiff filed the petition for certiorari, the caption will generally remain the same. If the defendant filed for certiorari, the caption in the case originally filed as Barry v. Crackpipe Industries, Inc. will look like this:





However, sometimes a lawsuit gets more complex, and parties take on dual roles, or new parties are added.

Intervenor: An intervenor is not originally a party to the lawsuit, but participates in a lawsuit already pending between two parties in several situations:

(1) when a statute of the United States confers an unconditional right to intervene; or

(2) when the applicant claims an interest relating to the property or transaction which is the subject of the action and the applicant is so situated that the disposition of the action may as a practical matter impair or impede the applicant’s ability to protect that interest, unless the applicant’s interest is adequately represented by existing parties.
This is known as Intervention of Right, where the party seeking to intervene (the "applicant") has a legal right to intervene in the pending lawsuit. Fed. R. Civ. P. 24(a)

There is a second set of circumstances under which a party may be permitted to intervene:

(1) when a statute of the United States confers a conditional right to intervene; or
(2) when an applicant’s claim or defense and the main action have a question of law or fact in common. When a party to an action relies for ground of claim or defense upon any statute or executive order administered by a federal or state governmental officer or agency or upon any regulation, order, requirement, or agreement issued or made pursuant to the statute or executive order, the officer or agency upon timely application may be permitted to intervene in the action. In exercising its discretion the court shall consider whether the intervention will unduly delay or prejudice the adjudication of the rights of the original parties.

This is known as "Permissive Intervention," Fed. R. Civ. P. 24(b).

Cross and Counter

Counterclaimant / Counter-plaintiff / Counterclaim Plaintiff: A defendant who responds to the plaintiff's suit by raising a cause of action against the plaintiff.

Crossclaimant / Cross-plaintiff / Crossclaim Plaintiff: A defendant or plaintiff who raises a cause of action against a codefendant/coplaintiff.

The English situation

The terminology for the parties to civil litigation in England has recently changed, so one now needs to understand the historical terms that have been used since the use of modern English, and the new terms. The terms "prosecution" and "defendant" have been retained for criminal litigation.

"The suer"

New style
Old Style
"Suing" or "bringing suit" is now known as "Claiming", or appropriate variants thereof.

"The sued"

New style
Old Style

"The appealer"

This is still the "appellant".

"The appealed against"

This is still the "respondant".


In the High Court, where the respondant counter-claims against the claimant on a related matter, the two claims may be joined and heard as part of one case, with only one case number issued, and one court process: In these cases, whoever brought claim first is the claimant (not that it matters very much in such cases). This tends to happen in patent infringement cases, where the respondant often counter-claims for the patent to be struck down.

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