HDI may refer to:* Human Development Index, a United Nations measure of well-being in a country Help Desk Institute, a trade association PSA HDi engine, a diesel automobile engine by Peugeot/Citroën Hexamethylene diisocyanate, an organic compound used to make polymers such as polyurethane HDi Interactive Format (formerly iHD), a trademark for Microsoft's implementation of advanced interactivity for HD DVD Histone deacetylase inhibitor, compounds used in psychiatry and neurology, and wi… (More on Hdi)