What term describes the skin surrounding, touching, and overlapping the nail on three sides?

The term that describes the skin surrounding, touching, and overlapping the nail on three sides is "perionychium." This anatomical term specifically refers to the area that creates a protective barrier around the nail, playing a crucial role in nail health by helping to prevent infection and injury.

In contrast, the lunula is actually the visible part of the matrix at the base of the nail, appearing as a crescent-shaped white area, and serves as a region where new nail cells are produced. The eponychium refers only to the portion of the stratum corneum that overlaps the nail plate at the base and can often be confused with the cuticle, which is actually the dead tissue at the nail's base. These terms all describe different components of the nail unit, but perionychium distinctly highlights the entire area surrounding the nail, encompassing the skin on three sides.