Lunula

Lunula (from the Latin lunule, meaning little moon)

Thumb nail, showing the lunula

Lunula is the white crescent shaped area at the base of the human finger or toe nail. Lunula is most obvious in the thumb, though not everyone's lunula is clearly visible. A lack of visible lunula is sometimes associated with certain pathologic conditions as in Terry's nails, where the nails appear white with a characteristic ground glass appearance and no lunula. This condition, thought to be due to decreased vascularity with increased connective tissue in the nail bed, is frequently found in hepatic failure, cirrhosis, diabetes, congestive heart failure, hyperthyroidism, and malnutrition.