In law, an appeal is the process in which cases are reviewed by a higher authority, where parties request a formal change to an official decision. Appeals function both as a process for error correction as well as a process of clarifying and interpreting law.Although appellate courts have existed for thousands of years, common law countries did not incorporate an affirmative right to appeal into their jurisprudence until the 19th century. The idea of an appeal from court to court (as distinguished from court directly to the Crown) was unheard of in early English courts.English common law courts eventually developed the writs of error and certiorari as routes to appellate relief, but both types of writs were severely limited in comparison to modern appeals in terms of availability, scope of review, and remedies afforded.

Although some courts permit appeals at preliminary stages of litigation, most litigants appeal final orders and judgments from lower courts. A fundamental premise of many legal systems is that appellate courts review questions of law de novo, but appellate courts do not conduct independent fact-finding.Instead, appellate courts will generally defer to the record established by the trial court, unless some error occurred during the fact-finding process.Many jurisdictions provide a statutory or constitutional right for litigants to appeal adverse decisions.However, most jurisdictions also recognize that this right may be waived. In the United States, for example, litigants may waive the right to appeal, as long as the waiver is "considered and intelligent".

he appellate process usually begins when an appellate court grants a party's petition for review or petition for certiorari.Unlike trials, which many common law jurisdictions typically perform with a jury, appeals are generally presented to a judge, or a panel of judges.Before hearing oral argument, parties will generally submit legal briefs in which the parties present their arguments at length in writing.Appellate courts may also grant permission for an amicus curiae to submit a brief in support of a particular party or position.After submitting briefs, parties often have the opportunity to present an oral argument to a judge or panel of judges.During oral arguments, judges often ask questions to attorneys to challenge their arguments or to advance their own legal theories.After deliberating in chambers, appellate courts issue formal written opinions that resolve the legal issues presented for review.

The appellate process usually begins when an appellate court grants a party's petition for review or petition for certiorari.Unlike trials, which many common law jurisdictions typically perform with a jury, appeals are generally presented to a judge, or a panel of judges.Before hearing oral argument, parties will generally submit legal briefs in which the parties present their arguments at length in writing.Appellate courts may also grant permission for an amicus curiae to submit a brief in support of a particular party or position.After submitting briefs, parties often have the opportunity to present an oral argument to a judge or panel of judges.During oral arguments, judges often ask questions to attorneys to challenge their arguments or to advance their own legal theories.After deliberating in chambers, appellate courts issue formal written opinions that resolve the legal issues presented for review.

When considering cases on appeal, appellate courts generally affirm, reverse, or vacate the decision of a lower court.Some courts maintain a dual function, where they consider both appeals as well as matters of "first instance".For example, the Supreme Court of the United States primarily hears cases on appeal but retains original jurisdiction over a limited range of cases.Some jurisdictions maintain a system of intermediate appellate courts, which are subject to the review of higher appellate courts.The highest appellate court in a jurisdiction is sometimes referred to as a "court of last resort".