DJIA or Dow refers to the Dow Jones Industrial Average, a stock market index that measures the performance of 30 large publicly traded companies listed on the New York Stock Exchange (NYSE) and the NASDAQ. The DJIA is one of the oldest and most widely followed stock market indices in the world, and it is often used as a barometer of the overall health of the US stock market and the US economy. The index is calculated by adding up the stock prices of its 30 constituent companies and dividing the sum by a divisor, which is adjusted periodically to account for changes in the stock market.