A symphony is the name of a type of classical music (a long, complex sonata) and the large orchestra that plays that music.
If you go to a concert hall to see a piece of Beethoven or another composer, you're going to hear a symphony — a type of complicated, orchestral music played by a symphony orchestra. A symphony usually includes strings, horns, drums, piano and has a conductor to lead the group by waving a baton. You can also use this word as a comparison: A gorgeous spring day could be called a symphony of beauty and new life.
