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.
Younger Years. Inventor Thomas Alva Edison was born on February 11, 1847, in Milan, Ohio. He was the last of the seven children of Samuel and Nancy Edison. Thomas's father was an exiled political activist from Canada. His mother, an accomplished school teacher, was a major influence in Thomasâ early life.