A ring is an ornamental band of metal or other durable material worn around the finger as an accessory. Rings may be used as symbols of love, engagement or commitment. They can be made from almost any hard substance and may be set with gems or other decorative materials. The term ring also refers to a circlet, hoop, or bangle, all of which are usually round but can be any shape. Other types of rings include neck rings, arm rings and toe rings. Rings may be worn as jewellery, as part of a costume or to signify an accomplishment. A ring is also a symbol of victory in sports competitions such as the Super Bowl or World Series. In the past, students and alumni of universities were given gold rings to commemorate graduation.
In many video games, a ring is a piece of equipment that prevents the user from being defeated, especially when the gamer is unshielded or non-invulnerable. The holder of the ring is protected against damage from enemy attacks or falling into bottomless pits and other dangers that would otherwise be deadly to them.
The ring is often associated with religious vows, such as those of virginity and marriage in some cultures. During the time of the ancient Egyptians, the ring was a sacred item that symbolized the union between a god and man. The ring could also be a sign of devotion, such as when worn by members of a monastic order or by some members of the clergy.
Throughout history, the ring has been worn as a sign of friendship, courtship and romance. In modern times, the ring is often given to a woman as a sign of her acceptance of a proposal of marriage. The ring is also a common symbol of fidelity among married couples.
In mathematics, a ring is a closed set that is closed under the operations of addition and multiplication and is an Abelian group with respect to addition and an associative semigroup with respect to multiplication. A ring that has multiplicative identity is called a ring with unity. Rings with multiplicative identities are not rare and can occur in algebraic fields. Several authors, such as Artin, Bourbaki, Eisenbud and Lang, depart from the normal convention by not requiring a 1 in the definition of ring. Most books published up to 1960 followed Noether’s convention, but the inclusion of a 1 has become more widespread since then.