What is the function of a lip liner?

The function of a lip liner is primarily to define the lip shape and prevent lipstick from feathering. When applied to the outer edges of the lips, a lip liner helps to create a clear boundary that enhances the overall shape and appearance of the lips. This definition can make the lips look fuller and more polished.

In addition to shaping, lip liners also serve a crucial role in keeping lipstick in place. They create a barrier that reduces the likelihood of color bleeding into the surrounding skin, especially with more creamy or emollient lipsticks that may tend to feather out over time. This function is important for maintaining a neat and long-lasting lip look throughout the day.

The other options do not align as directly with the primary purpose of a lip liner. While shine, exfoliation, and gradient effects can be achieved through various other products and techniques, they do not specifically relate to the primary role of lip liners in defining the lips and ensuring the longevity of lip color.