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.
(Äd'Ä­-sÉn) American inventor and physicist who took out more than 1,000 patents in his lifetime. His inventions include the telegraph (1869), microphone (1877), and light bulb (1879). He also designed the first power plant (1881-82), making possible the widespread distribution of electricity. During World War I, Edison worked on a number of military devices, including flamethrowers, periscopes, and torpedoes.