Amicus curiae
Amicus curiae: Latin for "friend of the court." A person or organization that is not a party but files a brief to offer information or arguments to the court. Federal Rule of Appellate Procedure 29 governs amicus briefs in the federal courts of appeals.
What amicus curiae means
Put simply, amicus curiae is part of the working vocabulary of a civil case. The short definition above covers the usual meaning. Still, a specific rule, statute or contract can give it a narrower meaning. For that reason, check how it is used in your own documents.
Where amicus curiae comes up
For example, the term appears in these procedures:
- Motion for Leave to File an Amicus Brief (Fed. R. App. P. 29): a request by a non-party, a "friend of the court," to file a brief that offers information or arguments the parties may not cover. Under Rule 29(a)(2), the United States, its officers and agencies, and a state may file an amicus brief without consent or leave. Any other amicus may file only by leave of court or if the brief states that all parties consented.
How to research the term
First, read the term where it actually appears. A rule, statute or court decision may define it for its own purposes. Next, check whether your court has a local rule that uses amicus curiae in a special way. Then look at recent decisions from courts in your jurisdiction. They show how judges apply the term today. Also, remember that state law can differ from federal law. For that reason, use our state procedures guide to find your state’s rules. Finally, confirm every source is current before you rely on it.
You can read the official rule text online for free.
Related legal terms
- Affirmative defense: a defense that defeats or reduces a claim even if the plaintiff's allegations are true, such as the statute of limitations.
- Agreement: a manifestation of mutual assent by two or more persons (Restatement (Second) of Contracts § 3).
- Allonge: a paper affixed to a negotiable instrument, treated as part of the instrument for indorsements.
- Amendment: a formal change or addition to a legal document.
Why precise terms matter
Courts read legal terms closely. As a result, knowing the exact meaning of a word helps you follow orders, rules and filings. Each glossary entry on Lawtopolis is short on purpose and links to the pages where the term is used.
Sources
Sources last reviewed: 2026-10-24
Lawtopolis provides legal information and education, not legal advice. Using this site does not create an attorney-client relationship. Laws and court rules vary by jurisdiction and change over time; verify every authority against the official source and consult a licensed attorney in your jurisdiction about your situation.