A toenail is the hard, protective covering that grows at the end of each toe, made from the same material as fingernails: a tough protein called keratin. Just as fingernails protect the sensitive tips of your fingers, toenails shield your toes from stubbing, pressure, and injury.

Toenails grow continuously from the base, pushing forward slowly over weeks and months. Because they keep growing, you need to trim them regularly to keep them from becoming too long or uncomfortable inside your shoes. Athletes, especially runners and soccer players, sometimes lose toenails temporarily when their shoes rub repeatedly against their toes during intense activity. The nail usually grows back over several months.

The phrase “fighting tooth and nail” means fighting with everything you have, using even your teeth and nails as weapons if necessary. While this expression refers to fingernails more than toenails, it shows how nails have long been seen as natural tools and defenses. Toenails might seem like a small detail of your body, but without them, walking and running would be considerably more painful.