modus operandi /op-ər-anˈdī or -anˈdē/ noun

Mode of operation, way of working

modus vivendi /vi-venˈdī or -dē (also wē-wenˈdē)/ noun

1. Way of life or living
2. An arrangement or compromise by means of which those who differ may get on together for a time
3. Such an arrangement between states or between a state and the Pope