A chain is a unit of length. It measures 66 feet, or 22 yards, or 100 links, or 4 rods (20.1168 m). There are 10 chains in a furlong, and 80 chains in one statute mile. An acre is the area of 10 square chains (that is, an area of one chain by one furlong). The chain has been used for several centuries in Britain and in some other countries influenced by British practice.

The chain was commonly used with the mile to indicate land distances and in particular in surveying land for legal and commercial purposes. In medieval times, local measures were commonly used, and many units were adopted that gave manageable units; for example the distance from London to York could be quoted in inches, but the resulting huge number would be unmemorable. The locally used units were often inconsistent from place to place.

In 1620, the clergyman Edmund Gunter developed a method of surveying land accurately with low technology equipment, using what became known as Gunter's chain; this was 66 feet long and from the practice of using his chain, the word transferred to the actual measured unit. His chain had 100 links, and the link is used as a subdivision of the chain as a unit of length.

A chain is a series of connected links which are typically made of metal. A chain may consist of two or more links.

Chains are usually made in one of two styles, according to their intended use:

Two distinct chains can be connected using a quick link which resembles a carabiner with a screw close rather than a latch.

Uses for chain include:

According to the "Complete Guide to Chain", the metal link chain was invented in 225 BC.

Unit may refer to:

Tory Gassway (born December 16, 1979), is an American rapper and actor, better known as Big Bad 4-0 formerly known as 40 Glocc. He is currently signed to Infamous Records and G-Unit Records. He is also an artist of G-Unit West.

Tory Gassway was born in Galveston Texas on December 16, 1979. At the age of eight he moved with his mother to various locations in California, until finally settling in the Inland Empire district of Colton also known as "The Zoo". There, he joined the local set of the Crips gang known as the Colton City Crips, though during an injunction against the Crip set, he later denied his involvement in the gang. He then began to rap with local friends and by 1997, his group, the "Zoo Crew", were recording and promoting their first album, Migrate, Adapt or Die, produced by Tony G and Julio G.

Big Bad 4-0 negotiated a deal with Empire Musicwerks, with distribution by BMG. It was through this deal, he recorded and released his first solo effort, "The Jakal", which featured such guests as, Bad Azz, Tray Deee, Ras Kass, Kurupt, Mac Minister, Spice 1 and several others; and such producers as Battlecat and Dr. Dre among several others. It was after this album that he decided to part ways with Empire Music.

Dwayne Michael Carter, Jr. (born September 27, 1982), better known by his stage name Lil Wayne, is an American rapper. At the age of nine, Lil Wayne joined Cash Money Records as the youngest member of the label, and half of the duo, The B.G.'z, with B.G.. In 1997, Lil Wayne joined the group Hot Boys, which also included rappers Juvenile, B.G., and Young Turk. Hot Boys debuted with Get It How U Live! that year. Lil Wayne gained most of his success with the group's major selling album Guerrilla Warfare, released in 1999. Also in 1999, Lil Wayne released his Platinum debut album Tha Block Is Hot, selling over one million copies in the U.S.

Although his next two albums Lights Out (2000) and 500 Degreez (2002) were not as successful (only reaching Gold status), Lil Wayne reached higher popularity in 2004 with Tha Carter, which included the single "Go D.J." Wayne also appeared on the Destiny's Child top ten single "Soldier" that year. In 2005, the sequel to Tha Carter, Tha Carter II, was released. In 2006 and 2007, Lil Wayne released several mixtapes and appeared on several popular rap and R&B singles. His most successful album, Tha Carter III, was released in 2008 and sold over 1 million copies in the U.S. its first week of release. It included the number-one single "Lollipop" featuring Static Major. It also includes the singles "A Milli" and "Got Money" featuring T-Pain and won the Grammy Award for Best Rap Album.