What can be sharp?

Many things can be sharp, but generally, when we say something is sharp, we're often referring to the edge or point of an object that is capable of cutting or piercing through another material with ease. Here are a few examples:

1. Knives: The edge of a knife is ground to be sharp so it can slice through food. 2. Scissors: The blades of scissors are sharp to make clean cuts through paper, cloth, and other materials. 3. Needles: The point of a needle is extremely sharp to penetrate fabric or skin when sewing or injecting medicine. 4. Broken glass: The edges of broken glass can be very sharp and can easily cut skin. 5. Razor blades: Used for shaving, the edges must be very sharp to cut through hair without pulling the skin. 6. Animal teeth or claws: Predators often have sharp teeth or claws to hunt or defend themselves.

The concept of sharpness is related to the geometry of the edge or point and the material's hardness. A sharper angle on the edge usually means the object can cut more easily, but this also tends to make the edge less durable.