A way, method, or mode of doing something; most commonly seen in the phrase 'modus operandi' meaning the way someone works.
From Latin 'modus' meaning manner or method. It's used in English primarily in legal and formal contexts, borrowed directly from Latin.
The phrase 'modus operandi' (literally 'method of operating') became famous in detective stories and crime investigation because it refers to the characteristic way a criminal commits crimes.
Complete word intelligence in one call. Free tier — 50 lookups/day.