A nail is horn- like envelope covering the dorsal aspect of the terminal phalanges of fingers and toes in humans.

Nails are similar to claws in other animals. The eponychium is the small band of epithelium that extends from the posterior nail wall onto the base of the nail. The perionyx is the projecting edge of the eponychium covering the proximal strip of the lunula. The skin dehydrates and tightens, making the nails appear to grow.