A world's fair, world fair, world exposition or universal exposition (sometimes spelled expo for short) is a large public exhibition. These exhibitions vary in character and are held in varying parts of the world. The next World's fair will be Expo 2015 in Milan, Italy.
Since the entering into force of the 1928 Convention Relating to International Exhibitions, the Bureau International des Expositions (BIE; English: International Exhibitions Bureau) has served as an international sanctioning body for world's fairs. BIE-approved fairs are of three types: universal,international, and specialized. They usually last from three weeks to six months.