nail

A nail is a small, long, thin sharp metal thing for holding wood together. People put it into the wood by hitting it with a hammer.

Example: I need some nails to fix the roof.

A nail is the thick, hard part at the ends of fingers and toes.

Example: I broke the top off my finger nail and it was very painful.

If you nail something to something else, you use a nail to join them.

Example: He nailed the set of shelves onto the wall.

When someone gets an idea just right, we say they nailed it or "hit the nail on the head".

Example: I think you've nailed the reason why this isn't working.