The Nikkei, officially known as the Nikkei 225, is a stock market index that represents 225 of the largest and most actively traded companies listed on the Tokyo Stock Exchange. It serves as a key indicator of the overall performance of the Japanese economy and is widely followed by investors and analysts. The index is calculated using a price-weighted method, meaning that companies with higher stock prices have a greater influence on the index's movements. The Nikkei includes major corporations from various sectors, such as automobiles, electronics, and finance, reflecting the diverse nature of Japan's economy.