A symphony is a large piece of music written for an orchestra (Like the New York Philharmonic, and the Boston Symphony Orchestra). They started with Haydn during the Classical period, and are still written today. They consist usually of 3 main movements, or sections each lasting several minutes. (the number does vary depending on composer-- Olivier Messiaen wrote one that is 10 movements long!).
See the related link 'Wikipedia - Symphony' to the left for further information.
Symphony is also a greek word which means "aggrement"
It comes from two words:Syn=Add and phoni=voice thus you have "added voices" equals aggreed voices...
or its Cinthya