The nail plate is the hard, translucent part of the nail that is made of tightly packed keratinised cells, which grows out from the matrix over the nail bed and is the surface polish is painted on.
Also known as: nail body, the nail, nail surface, corpus unguis
The nail plate is the part most people mean by the nail. It is made of hard, flattened, keratinised cells packed in layers. The germinal matrix at the base produces about 90 percent of it. The plate rests on the nail bed, which is firmly attached to it, and takes its shine from the roof of the nail fold it grows out under (Medscape).
Fingernail plates grow about 3 to 4 mm a month, and a full plate is replaced in roughly 6 months. Toenails grow at about half that speed (Medscape). The plate has no blood supply of its own. It receives nutrients from the nail bed and matrix beneath it.
The plate is porous. It swells in water and shrinks as it dries, which is why long soaks before painting lead to chips, and why hot water loosens polish. Strong pigments can migrate into it and stain it yellow. A base coat blocks them. Solvents and acetone dry it, so oil after removal keeps it flexible.
Changes in the plate record what happened at the matrix weeks earlier: white spots from knocks, horizontal grooves from illness or trauma, vertical ridges from ageing. Peeling at the free edge shows the layers separating. A change that appears on several nails at once is a reason to see a GP or dermatologist (Mayo Clinic).