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.
In honor of his birthday (he was born in February 11, 1847), Neatorama has cobbled up 10 fascinating facts about Thomas Edison, the world's most famous and prolific inventor: Edison was an inquisitive child but a poor student as his mind often wandered.