In law, authorization in writing empowering a person to perform an act or execute an office.
Arrest warrants are necessary (except in certain circumstances) for an arrest to be considered legal. Search warrants entitle the holder to enter and search a property. Both are classes of judicial warrants. To obtain them, a complainant must provide an affidavit setting forth facts sufficient to satisfy the belief that a crime has been committed and that the accused is the guilty party (or, in the case of the search warrant, that the place to be searched will yield the expected evidence). Nonjudicial warrants include tax warrants (which provide the authority to collect taxes) and land warrants (which entitle the holder to a specific tract of public land).