Ring (noun)

1. A circular band of metal or other material worn around the finger.
2. A circular band of metal or other material used as a decoration or symbol of authority.
3. A circular piece of metal or other material used in a machine or tool.
4. A circular area in which something is located or operates.
5. A sound made by a bell or a similar instrument.

Origin:

Old english hring, of germanic origin; related to dutch ring and german ring.

Examples:

1. She wore a gold ring on her finger.
2. The Pope wears a ring as a symbol of his authority.
3. The piston is fitted with a ring to prevent oil leaks.
4. The nuclear reactions take place in a tiny ring at the center of the reactor.
5. The sound of the church bell ringing filled the air.