What is not a wind instrument?

The answer is Viola because it is not a wind instrument. The viola is a string instrument that is played with a bow, similar to a violin. It belongs to the string family along with instruments like the cello and double bass. Wind instruments, on the other hand, produce sound by the vibration of air, such as through the use of breath or blowing into the instrument. Therefore, the viola does not fit within the category of wind instruments.