A ring is an algebraic structure that generalizes fields. It consists of a set equipped with two operations, addition and multiplication, that satisfy properties analogous to those of the integers: the additive inverse of any element in the ring is unique, the operation of multiplication distributes over the operation of addition, and addition is commutative. Rings can contain numbers as well as non-numerical objects such as polynomials, matrices and functions.
Historically, rings have been used to symbolize union and loyalty—especially between husband and wife, or in the case of professional boxers, between trainers and their charges. Rings are typically worn on the finger, but may also be affixed to other parts of the body. In mathematics, a ring is also a geometric object, and can be recovered from the abstract properties of its elements, by restricting to functions that preserve certain geometric properties such as continuity and differentiability.
The earliest known use of the word is in the Bible, where it refers to the rings through which staves were passed in the ark (Exodus 25:12). In the Hebrew language, tabbaath means “sink,” either because it is cast or because it sinks into the material on which it is impressed, such as wax or clay, and hence leaves an impression.
Since then, the ring has been used in many different cultures around the world to symbolize a variety of things. Often, the ring is symbolic of a marriage or betrothal, and in some cultures it may also signify a membership in an organization or community. In Western culture, a wedding or engagement ring is usually made of precious metal. The ring may be set with gemstones, diamond being the most common.
A more informal term for a ring is a band, and it is this form that most people think of when they hear the word. A ring may be made of any type of durable material and can be worn on the finger or other part of the body. A ring may be set with gems or diamonds, but it is more commonly made of gold or another precious metal and worn as jewelry. It can be worn on the ring finger, pinky finger, or even as a nose or eyebrow piercing.
A ring can be used to measure the circumference of the ring finger, but this method is not very accurate. A much better way is to use string, which can be wrapped comfortably around the ring finger, and then to mark the point at which the string overlaps. This measurement can then be compared to a ring size chart to determine the correct sizing for the person. If a ring is too loose, it will cause discomfort and the wearer’s knuckles may be bumped or marked by the edges of the ring. If it is too tight, it can cause irritation and the ring can rub against the skin causing blisters. This is why it is important to find a ring that fits snugly on the base of the knuckle.