Nail

noun

1. The thin, horny plate at the ends of fingers and toes on humans and some other animals.

   "When I'm nervous I bite my nails."

2. The basal thickened portion of the anterior wings of certain hemiptera.
3. The terminal horny plate on the beak of ducks, and other allied birds.
4. The claw of a bird or other animal.
5. A spike-shaped metal fastener used for joining wood or similar materials. The nail is generally driven through two or more layers of material by means of impacts from a hammer or other device. It is then held in place by friction.