A deficit is the amount by which a sum falls short of some reference amount.

• Deficit (economics), the excess of an organization's expenditure over its revenue

• Attention deficit hyperactivity disorder, a developmental disorder
• Cognitive deficit, any characteristic that acts as a barrier to cognitive performance

• Defect (geometry), angular deficit
• Déficit, a 2007 Mexican film by Gael García Bernal

• Government debt, the accumulated amount of deficits; "debt" and "deficit" are sometimes confused.
• Deficit Reduction Act (disambiguation)
• Deficit reduction
• Fiscal (disambiguation)