A responsibility-assignment matrix that classifies every person involved in a task or decision into one of four roles: Responsible (does the work), Accountable (owns the outcome — exactly one person per task), Consulted (provides input before the work is done), and Informed (notified after the fact). RACI is the most widely used clarity tool in project management because it surfaces the two most common organizational failure modes: multiple accountabilities (which produce conflict) and zero accountabilities (which produce drift).
