Knife (noun)

1. An instrument consisting of a sharp blade fixed into a handle, used for cutting and spreading food, for cutting hair and nails, for cutting paper and cloth, etc.
2. A weapon consisting of a sharp blade fixed to a handle, used for cutting or thrusting.
3. A surgical instrument with a sharp blade used for cutting or dissecting tissue.

Origin:

Old english cnif, of germanic origin; related to dutch and german messer.

Examples:

1. She pulled a knife from her pocket.
2. He was arrested for carrying a knife.
3. I need to sharpen my knife before I can use it.
4. This knife is perfect for slicing tomatoes.
5. The surgeon used a knife to make an incision.