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 Edisonâs Top 5 Tips for Success. Thomas Alva Edison was one of the most famous and hard-working inventors in history. When he died in 1931 he held 1093 patents in his name (though a lot of his inventions were collaborations). Some of his most used inventions are of course the light bulb and the gramophone.