Stock Market Crash of 1929: The catastrophic collapse of stock prices on Wall Street in October 1929, which marked the beginning of the Great Depression.
Great Depression: A severe worldwide economic downturn that lasted from 1929 to the late 1930s characterized by high unemployment rates, bank failures, poverty, and a general decline in business activity.
Black Tuesday: The specific day - October 29th, 1929 - when stock prices plummeted drastically during the Stock Market Crash.