What is the scientific name for the natural nail, which is composed mainly of keratin?

The term "natural nail" refers to the entire structure that forms the fingernail or toenail. The natural nail is primarily composed of keratin, a tough protein that provides strength and resilience. This composition allows the nail to protect the distal phalanx (the fingertip bone) and enhance the dexterity of fingers and toes.

While "nail plate" refers specifically to the hard, visible part of the nail that sits on top and is made of keratin, it does not encompass the entirety of the nail structure as "natural nail" does. The "lateral nail fold" pertains to the skin folds on each side of the nail plate that help protect it, but again, does not represent the nail itself. The "lunula" is the crescent-shaped area at the base of the nail plate, which is just a small part of the overall structure.

Thus, "natural nail" is the term that accurately describes the entire entity made mostly of keratin, making it the most appropriate choice in this context.