Which term refers to overgrowth of the cuticle onto the nail plate?

The term that refers to the overgrowth of the cuticle onto the nail plate is pterygium. Pterygium occurs when the skin or cuticle grows abnormally over the nail plate, potentially affecting the appearance and health of the nail. This condition may arise from various factors, including trauma, infection, or chronic exposure to irritants.

Understanding the other terms helps clarify why pterygium is the correct choice. The eponychium is the area of skin at the base of the nail that lies above the nail matrix and is often confused with the cuticle; however, it is not the term for overgrowth onto the nail plate itself. The hyponychium refers to the skin located beneath the nail tip, and it is also not related to cuticle overgrowth. Onychia denotes an inflammation of the nail matrix, which could lead to nail shedding or deformity but does not describe the condition of the cuticle overgrowing onto the nail plate. Thus, pterygium is the specific term used for that situation.