Which disorder is characterized by the nail growing into the edge of the nail grooves?

Onychocryptosis, also known as an ingrown toenail, is specifically characterized by the nail growing into the edge of the nail grooves, which can lead to pain, inflammation, and infection. This condition often occurs when the corners or sides of the nail dig into the surrounding skin, causing discomfort and sometimes requiring medical intervention.

In understanding the context of nail disorders, it's clear that onychomalacia refers to the softening of the nails, often associated with various health conditions but not related to the growth pattern described. A fungal infection would lead to discoloration and thickening of the nail rather than the abnormal growth into the skin. Onycholysis involves the separation of the nail plate from the nail bed, which presents differently from the defining characteristics of onychocryptosis. Thus, it is the unique growth pattern of the nail in onychocryptosis that identifies it as the correct response.