<unk>  (or<unk> , is a medical term for white discoloration appearing on nails. It is derived from the Greek words leuko 'white' and onyx 'nail'. The most common cause is injury to the base of the nail (the matrix) where the nail is formed.
Leukonychia
Melanonychia
Paronychia
Chromonychia
Platonychia
Anonychia
Trachonychia
Hapalonychia