phrase
Latin
Modus Operandi (M.O.)
lit. โway of operatingโ
Someone's characteristic method of doing something.
Origin
Came into English through 19th-century criminology, where it described a criminal's signature methods. The abbreviation 'M.O.' is now standard in detective fiction.
Modern usage
Crime stories use it literally; everyone else uses it loosely ('her M.O. is to ghost you for a week and then send a meme').
Tags
pattern
behavior