An ingrowing toenail grows inwards at the side of the toe, cutting into the skin. It hurts, and it can become infected. In British English people say ingrowing toenail; in American English the usual form is ingrown toenail, same problem. The word is almost only used with nails — toenails especially, sometimes fingernails. You would not call a tree ingrowing. Doctors and everyday speakers both use it; it is not fancy, just a bit medical.

嵌甲的（指甲往肉裡長；英式說 ingrowing toenail，美式較常說 ingrown）