Final answer:
A healthy nail matrix will replace a lost nail due to injury in about six months, although the rate of regrowth can vary based on individual circumstances.
Step-by-step explanation:
When a nail is lost due to injury, the nail matrix must be healthy for the nail to regrow. If the matrix remains healthy, a nail lost through injury will be replaced in about six months. Fingernails grow quicker than toenails, but the actual rate can vary depending on individual health factors, age, season, diet, and genetic factors. Typically, fingernails grow at a rate of about 3mm per month, meaning that complete replacement usually takes approximately half a year, while toenails grow at about 1mm per month, which can require up to 18 months for complete regrowth.