Mous operandi (often used in the abbreviated forms M.O. or simply Method) is a Latin phrase, approximately translated as "mode of operation". The plural is modi operandi ("modes of operation"). It is used in law enforcement to describe a criminal's characteristic patterns and style of committing crimes. It is also applied in fraud investigation when speaking of behavior patterns that indicate specific types of fraud, e.g., "False identity is a key MO of retail banking sleeper fraud".