1. Anatomy:
* The joint between a finger or toe bone and the next bone: This is the most common usage. We talk about "knuckles" on our hands and feet. It's the bony prominence that we can feel when we bend our fingers.
2. Actions:
* To bend or flex a finger or fingers: For example, "He knuckled his fingers in anticipation."
* To rap or knock with the knuckles: For example, "He nervously knuckled on the door."
3. Slang:
* Hard work: For example, "We had to knuckle down to get this project finished."
* A small amount of money: For example, "I only have a few knuckles to my name."
4. Other:
* A part of a machine that resembles a knuckle: This is often seen in engineering or technical contexts.
* A knot in wood: This is a less common usage, but it can refer to a hard, knotty area in wood.
The specific meaning of "knuckle" is determined by the context in which it is used.