Great Depression: This was a severe worldwide economic depression that took place during the 1930s. It began in the United States, but had severe effects around globe.
Stock Market Crash: This is when there is a sudden dramatic decline of stock prices across a significant cross-section of a stock market. The crash in 1929 triggered Great Depression.
New Deal: A series of programs, public work projects, financial reforms, and regulations enacted by President Franklin D. Roosevelt in United States between 1933-39 to respond to needs for relief from Great Depression.