What is the term for the white area shaped like a crescent moon on a nail?

The term for the white area shaped like a crescent moon at the base of a nail is known as the lunula. This anatomical feature is visible at the proximal end of the nail and is a part of the nail matrix from which the nail grows. The lunula can be seen more prominently on some nails while less so on others, and it varies in size and visibility from person to person.

Understanding the structure and appearance of the lunula is important in various fields, including dermatology and medical coding, as changes in its appearance can indicate health issues. The other terms listed refer to different conditions or structures: onycholysis is the separation of the nail from its bed, Beau's lines represent transverse grooves in the nail indicative of nail growth disruption, and a cyst is a sac-like structure that can occur in various body tissues.