DEFINITION of 'Purchasing Power Parity-PPP'. An economic theory that estimates the amount of adjustment needed on the exchange rate between countries in order for the exchange to be equivalent to each currency's purchasing power.
Thomas Edison's most famous invention, the lightbulb, paved the way for modern life.
Did You Know? By the time he died on October 18, 1931, Thomas Edison had amassed a record 1,093 patents: 389 for electric light and power, 195 for the phonograph, 150 for the telegraph, 141 for storage batteries and 34 for the telephone.