Final answer:
The crescent-shaped white area at the base of the nail body is called the lunula, a visible portion of the nail matrix indicating where the nail begins to form and is surrounded by the nail root and matrix.
Step-by-step explanation:
The crescent-shaped white area at the base of the nail body nearest the root is known as the lunula. The lunula is a visible part of the nail matrix, where a thick layer of epithelium forms this distinctive white region. Its primary function is to define the free edge of the nail matrix, where the nail starts to form. The nail root, located beneath the surface of the skin, is where the nail begins. It is surrounded by the nail matrix, which contains the stem cells responsible for producing keratinocytes that constitute the nail. As the matrix produces new nail cells, the older ones are pushed outward and they become hard and compact to form the nail body. The nail body, being composed of densely packed dead keratinocytes, appears pink due to the underlying blood vessels, except for the lunula.