What type of tool is best for creating defined curls?

The curling iron is specifically designed to create defined curls by utilizing heat and a cylindrical barrel. This tool allows the stylist to wrap sections of hair around the heated barrel, which effectively shapes the hair into curls or waves. The various sizes of barrels available enable stylists to achieve different curl types, from tight ringlets to loose, beachy waves, depending on the desired look.

In contrast, a flat iron is primarily used for straightening hair, as it comprises two flat plates that clamp down on the hair to smooth it out. A blow dryer helps in drying hair and can be used with styling techniques to create volume but does not inherently curl hair. Lastly, a round brush is commonly used during blow-drying to add volume and shape to the hair, but it does not produce defined curls like a curling iron does. Thus, for achieving defined curls effectively, the curling iron is the most suitable tool.