Recession
A sustained decline in economic activity, conventionally defined as two consecutive quarters of negative GDP growth.
A recession is a significant, broad-based decline in economic activity lasting more than a few months. The most-cited rule of thumb is two consecutive quarters of negative GDP growth, though more rigorous definitions consider multiple indicators including employment, real income, retail sales, and industrial production.
Recessions are typically caused by some combination of asset bubbles bursting, financial system failures, central bank tightening to fight inflation, supply shocks, or confidence collapses. Effects include rising unemployment, falling investment, declining asset prices, and increased government deficits.
Modern recessions in advanced economies typically last 6-18 months, with longer recovery periods. They're a normal feature of market economies that have appeared roughly every 5-10 years for the past century.