Noun > modus operandi

This term is Latin for “way of operating.”

A modus operandi, often abbreviated as MO or M.O., is a normal, typical way of doing some task.

MO duss OPP er AN dee
(Or, if you prefer, pronounce the last syllable as “dye” and say “MO duss OPP er AN dye.”)

Part of speech:
Noun, the countable kind: “her modus operandi,” “these modi operandi.”

Other forms:
Notice how the plural is “modi operandi.”

How to use it:
This term can sound formal when you say or write it in full–and it can sound very casual when you abbreviate. “That’s my M.O., man.”

Talk about the modus operandi of a specific person, group, company, party, industry, etc. Or, talk about the modus operandi of something nonhuman, like a drug, a disease, a bodily organ, a predator, a computer virus, etc.

Your tone can be neutral: “Internal competition is their modus operandi.”

Or it might be critical: “Their modus operandi has always been violence.” (In fact, we use “modus operandi” very often in reference to crimes and manipulation.)

Or, your tone might be complimentary: “His modus operandi is to sum up his opponent’s argument with the greatest of nuance, accuracy, and eloquence before raising objections to it.”

“Constant motion, literal and figurative, is (Rickie Lee) Jones’ modus operandi. ‘I’ve always liked to run away,’ she told Rolling Stone in 1979.”
— Alison Fensterstock, The Los Angeles Times, 13 June 2019

“The modus operandi was to join a caravan and become accepted as bona-fide travellers themselves. The Thugs would need to delay any attack until their fellow travellers had dropped the initial wariness of the newcomers…”
— Entry on “Thuggee” (a type of assassin), World Heritage Encyclopedia