Persuasive authority describes legal sources that a court may, but is not required to, follow when interpreting the law or deciding a case. It contrasts with binding precedent. The term is descriptive rather than formally defined in legislation or case law, but is widely used in civil and common law reasoning across the UK and Ireland. Persuasive authority typically includes: decisions of courts in other UK or Irish jurisdictions (for example, Irish Supreme Court decisions in English courts), judgments from the Privy Council, lower‑level or coordinate courts, obiter dicta, foreign case law from other common law systems, academic writing, Law Commission or Law Reform Commission reports and, in some contexts, regulatory guidance. Courts in England and Wales, Scotland, Northern Ireland and Ireland assess persuasive weight by reference to the status of the source, quality of reasoning, similarity of legal framework and factual comparability. Higher appellate courts’ obiter dicta and closely reasoned comparative common law judgments are often given significant persuasive value. Usage of the term “persuasive authority” is broadly consistent across all four jurisdictions and is central to legal research, advocacy and judicial development of the common law.