A permanent body wave, also known as a perm, uses chemical processes to change the shape of the hair from straight to curly or wavy. Body waves often have less curl than other types of perms as they are intended to add volume and only a small amount of wave.
According to Elle, body waves soften women's facial features and create more hair volume and texture when done properly. To get optimal volume and wave without adding much curl, stylists use large perm rods and a softer perm solution. Since the amount of curl achieved directly correlates to the size of the perm rods, smaller rods are not used in wave perms as they create more curl.