Modus operandi

A modus operandi (often shortened to M.O., MO, or just modus; Latin pronunciation: [ˈmɔ.dʊs ɔ.pɛˈran.dɪ]) is an individual's habits of working, particularly in the context of business or criminal investigations, but also generally. It is a Latin phrase, approximately translated as 'mode (or manner) of operating'.¹

The term is often used in police work when discussing crime and addressing the methods employed by criminals. It is also used in criminal profiling,² where it can help in finding clues to the offender's psychology.³ It largely consists of examining the actions used by the individuals to execute the crime, prevent its detection and facilitate escape.¹ A suspect's modus operandi can assist in their identification, apprehension, or repression, and can also be used to determine links between crimes.⁴

In business, modus operandi is used to describe a firm's preferred means of executing business and interacting with other firms. Also in a person’s routine patterns of action and decision‑making in normal situations, revealing their typical operating style.

The plural is modi operandi.⁵⁶ The word operandi is a gerund in the genitive case, "of operating"; gerunds can never be pluralised in Latin, as opposed to gerundives. When a noun with an attribute in the genitive is pluralised, only the head noun normally changes, just as in English with "of": "a fact of life, two facts of life" (unlike, for instance, les modes opératoires in French).