Toxicity is the second album by American heavy metal band System of a Down. Produced by Rick Rubin, Toxicity was released on September 4, 2001 by American Recordings, debuting at number 1 on both the United States, with 220,000 copies, and number 1 on the Canadian charts. Toxicity has sold over 12 million copies worldwide and is multi-platinum in the United States. The band have mentioned the ironic predicament of the album being released exactly one week before 9/11 on numerous occasions.

The album is listed in Blender's 500 CDs You Must Own.MusicRadar held a public poll and Toxicity was ranked as 28th greatest heavy metal album in the list of The 50 Greatest Heavy Metal Albums of All Time. The album is ranked at number 44 in Rolling Stone's 100 Best Albums of the Decade for 2000s.

Digital Dream Door has currently ranked Toxicity at number 72 on their list of the "100 Greatest Metal Albums", and number 16 on their list of "100 Greatest Albums of the 2000s". Alternative Press ranked it number 9 in its "25 Best Albums of 2001" (Feb 2002, p.64). Mojo ranked it number 93 in its "100 Modern Classics" (p.54).

Toxicity is the degree to which a substance can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell (cytotoxicity) or an organ such as the liver (hepatotoxicity). By extension, the word may be metaphorically used to describe toxic effects on larger and more complex groups, such as the family unit or society at large.

A central concept of toxicology is that effects are dose-dependent; even water can lead to water intoxication when taken in too many doses, whereas for even a very toxic substance such as snake venom there is a dose below which there is no detectable toxic effect. Toxicity is species-specific, lending cross-species analysis problematic. Newer paradigms and metrics are evolving to bypass animal testing, while maintaining the concept of toxicity endpoints.

There are generally three types of toxic entities; chemical, biological, and physical:

An album may be understood as a collection of recordings, released as a single package on gramophone record, cassette, compact disc, or via digital distribution, however the concept is found in printed music dating into the early nineteenth century in works by composers such as Schumann and Mendelssohn. The word derives from the Latin word for list.

Today, with the vinyl record no longer being used as the primary form of distribution, the term "album" can still be applied to any sound recording collection, such as those on compact disc, MiniDisc, Compact audio cassette, and digital or MP3 albums.Cover art is also considered an integral part of the album. Many albums also come with liner notes and inserts giving background information or analysis of the recording, reprinted lyrics, images of the performers, or additional artwork and text. These are now often found in the form of CD booklets.

Vinyl LP records have two sides, each comprising one half of the album. If a pop or rock album contained tracks released separately as commercial singles, these were often traditionally placed in particular positions on the album. A common configuration was to have the album led off by the second and third singles, followed by a ballad. The first single would lead off side 2. In the past many singles (such as the Beatles' "Hey Jude" and Bob Dylan's "Positively 4th Street") did not appear on albums, but others (such as the Beatles' "Come Together" and Dylan's "Like a Rolling Stone") were part of an album released concurrently. Today, many commercial albums of music tracks feature one or more singles, which are released separately to radio, TV or the Internet as a way of promoting the album. Albums have also been issued that are compilations of older tracks not originally released together, such as singles not originally found on albums, b-sides of singles, or unfinished "demo" recordings.

System of a Down, also known by the acronym SOAD and often shortened to System, is a rock band from Southern California, formed in 1994. It consists of Serj Tankian (lead vocals, keyboards, rhythm guitar), Daron Malakian (guitar, vocals), Shavo Odadjian (bass, background vocals) and John Dolmayan (drums).

The band achieved commercial success with the release of five studio albums; from which three debuted at number one on the Billboard 200. System of a Down has been nominated for four Grammy Awards, and won the award in 2006 for Best Hard Rock Performance for the song "B.Y.O.B.". The group went on hiatus in August 2006, but reunited in November 2010, embarking on a worldwide tour in 2011.

Serj Tankian, Daron Malakian, and Shavo Odadjian all attended Rose and Alex Pilibos Armenian School while children, although because of their eight-year age difference they did not meet until 1992 while working on separate projects at the same recording studio. They formed a band named Soil with Tankian on vocals and keyboards, Malakian on vocals and guitar, Dave Hakopyan (who later played in The Apex Theory/Mt. Helium) on bass and Domingo "Dingo" Laranio on drums. The band hired Shavo Odadjian (another Rose and Alex Pilibos alumnus) as manager, although he eventually joined Soil as rhythm guitarist. After three years, only one live show, and one jam session recording, Hakopyan and Laranio quit the band, feeling that it was not going anywhere.