If I had a nickel for every time this question was asked….
The main differences between a viola and violin are the size and strings. The largest a violin can be is 14″ (body length) whereas a viola can be as large as 19″. Second, while a violin has the strings labeled E,A,D,G the viola removes the E string and replaces it with a C string next to the G string. This allows the viola to take advantage of its larger body to provide a very mellow sound. For more, read our guide on what is a viola.