What common product can be used to help define curls?

Curl cream or mousse is effective for defining curls because these products are specifically formulated to enhance the natural texture of curly hair. They often contain ingredients that provide moisture and hold without weighing the hair down, allowing the curls to form more naturally and maintain their shape. Curl creams and mousses typically offer a combination of hydration and light hold, which is crucial for achieving well-defined, bouncy curls.

In contrast, hair gel can offer a strong hold, but it may also cause curls to become crunchy or rigid if too much is applied, which can detract from the natural look and feel of the curls. Hair spray is primarily used for setting styles and providing additional hold, but it is not designed to enhance curl formation. Leave-in conditioner provides moisture and helps with softness, but it lacks the necessary ingredients to specifically define curls the way curl creams or mousses do. Thus, curl cream or mousse stands out as the best option for achieving defined curls.