What is the purpose of a base coat in nail application?

The purpose of a base coat in nail application is primarily to protect the natural nail and improve the adhesion of polish. Applying a base coat acts as a barrier between the nail and the colored polish, which can prevent staining and discoloration of the natural nail. Additionally, it creates a slightly tacky surface that helps the colored polish adhere better, leading to a longer-lasting manicure. This adhesion is essential, as it can significantly reduce chipping and peeling of the polish over time.

The other options do play roles in nail application but do not reflect the primary function of a base coat. While base coats can sometimes create a subtle finished look, their primary objective is not to provide color or a glossy finish. Instead, that's the role of colored polish and topcoats, respectively. Enhancing nail length is also not a function associated with base coats, as length is typically addressed through nail extensions or artificial tips.