Pincer nails are known for what characteristic?

Pincer nails are characterized by being narrow at the free edge with inward-folding corners. This distinct shape often leads to a pointed or tapered appearance as the sides of the nail grow inward toward the center. This characteristic can cause discomfort and may affect the overall health of the nail and surrounding tissue, as the inward growth can create pressure against the skin.

While the other characteristics mentioned, such as an exaggerated deep "C" curve, a splitting or brittle texture, and loosening at the matrix, can pertain to different nail conditions or abnormalities, they do not specifically define pincer nails. Pincer nails emphasize the unique structural form where the free edge is narrower, making option A the most accurate representation of their defining trait.