Area Median Income (AMI) is the midpoint household income for a specific geographic region, meaning half of families earn more and half earn less, used primarily to determine eligibility for affordable housing and other federal/state programs. Calculated annually by the U.S. Department of Housing and Urban Development (HUD), AMI adjusts for household size, with various income levels (like 30%, 50%, 80% AMI) defining different tiers of affordability.