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.
Thomas Edison (1847â1931) American inventor who filed over 1,000 patents. He developed and innovated a wide range of products from the electric light bulb to the phonograph and motion picture camera. One of the greatest inventors of all time.