Single Source of Truth

A single source of truth is one agreed place where a particular piece of information officially lives, so everyone in the business refers to the same version rather than their own copy. If the customer list is the single source of truth, updating it there means every team sees the change, instead of five spreadsheets slowly drifting apart.

It is like a household keeping one shared calendar on the wall rather than each person keeping a separate diary and double-booking the car. This matters because conflicting copies of the same information cause wasted time, wrong decisions and arguments over whose numbers are right.