Lost property is typically defined as personal property that an owner unintentionally and involuntarily parts with.
Real property may not be lost or mislaid.
Common Law Origins
Common law defines lost property as personal property that was unintentionally left by its true owner. For example, a wallet that falls out of someone's pocket is lost.
At common law, a person who found lost personal property could keep it until and unless the original owner comes forward. This rule applied to people who discovered lost property in public areas, as well as to people who discovered lost property on their property.
Many jurisdictions have statutes that modify the common law's treatment of lost property. Typically, these statutes require lost personal property to be turned over to a government official, and that if the property is not claimed within a set period of time, it goes to the finder, and the original owner's rights to the property are terminated.