Joint (noun)

1. The point at which two or more bones are attached in the body.
2. A place or point where two or more things are joined or united.
3. A device or piece of equipment used to connect two or more things together.

Origin:

Middle english: from old french joint, past participle of joindre "to join", based on latin jungere.

Examples:

1. The joint in my finger hurts.
2. The joint of the pipe was leaking.
3. The roof had a joint that needed to be fixed.
4. This joint is the weakest point of the structure.
5. The joint venture between the two companies was successful.