The gray (symbol: Gy) is the SI derived unit of absorbed dose, specific energy (imparted) and of kerma. Such energies are typically associated with ionising radiation such as X-rays or gamma particles or with other nuclear particles. It is defined as the absorption of one joule of such energy by one kilogram of matter (usually human tissue).

The gray was named after the British physicist Louis Harold Gray, a pioneer in the field of measurement of radium radiation and X-rays and their effects on living tissue, and was adopted as part of SI by the 15th CGPM in 1975. The SI unit replaces the traditional cgs unit, the rad (equivalent to 0.01 Gy), which remains common in industry in the United States, while "strongly discouraged" in the style guide for U.S. National Institute of Standards and Technology authors.

One gray is the absorption of one joule of energy, in the form of ionizing radiation, per kilogram of matter.

For xrays and gamma rays, these are the same units as the sievert (Sv). For alpha particles one gray is twenty sievert. To avoid any risk of confusion between the absorbed dose (by matter) and the equivalent dose (by biological tissues), one must use the corresponding special units, gray is used instead of the joule per kilogram for absorbed dose and the sievert instead of the joule per kilogram for the dose equivalent. The word "gray" is both the singular and plural spelling.

Grey or gray is an achromatic or neutral color.

Complementary colors are defined to mix to grey, either additively or subtractively, and many color models place complements opposite each other in a color wheel. To produce grey in RGB displays, the R, G, and B primary light sources are combined in proportions equal to that of the white point. In four-color printing, greys are produced either by the black channel, or by an approximately equal combination of CMY primaries. Images which consist wholly of neutral colors are called monochrome, black-and-white or greyscale.

The first recorded use of grey as a color name in the English language was in AD 700.Grey is the British, Canadian, Australian, Irish, New Zealand and South African spelling, although gray remained in common usage in the UK until the second half of the 20th century.Gray is the preferred American spelling, although grey is an accepted variant.Gray became the preferred spelling in American English around 1825.

Most grey pigments have a cool or warm cast to them, as the human eye can detect even a minute amount of saturation.^{[citation needed]}Yellow, orange, and red create a "warm grey". Green, blue, and violet create a "cool grey". When there is no cast at all, it is referred to as "neutral grey", "achromatic grey" or simply "grey".

Unit may refer to:

Matthew Gray Gubler (born March 9, 1980) is an American actor, film director, painter, photographer, editor, and former fashion model. He is best known for his role as the young genius Dr. Spencer Reid in the CBS television show Criminal Minds, of which he has also directed three episodes. Gubler has also appeared in (500) Days of Summer as Joseph Gordon-Levitt's friend Paul. Gubler also is the voice of one of the chipmunks, Simon Seville, in Alvin and the Chipmunks, Alvin and the Chipmunks: The Squeakquel and Alvin and the Chipmunks: Chip-Wrecked. Gubler directed and created several movies that were mostly filmed in his hometown of Las Vegas as well as New York City, prior to his graduation from NYU.

Gubler is a high school graduate of the Las Vegas Academy of International Studies, where he majored in acting, because the school did not offer his first love, film making. He is a graduate of New York University's Tisch School of the Arts where he majored in film directing. He also attended UC Santa Cruz. Gubler's parents were both born in Las Vegas and his mother, Marilyn Gubler, was the first woman to serve as Republican state Chairman. His grandfather Maxwell Kelch was the first president of the Las Vegas Chamber of Commerce and founded Las Vegas' first radio station (KENO). Gubler's sister Laura Dahl is a fashion designer based in New York City. He has a brother named Gray Gubler who was born in 1994, who appeared in the music video for the song Reagan by Whirlwind Heat (which Gubler directed).

Matthew Gray (born 24 July 1973) is an athlete from Victoria, Australia. He competes in archery. He was an Australian Institute of Sport scholarship holder. .

Gray took up archery at the age of seven when his father bought a bow at a garage sale. After months of harassment, he took up archery. He was selected to be a part of the Australian team for the Junior World Field Championships in 1988 where he won a bronze medal. He won another bronze medal in 1994 at the senior World Field Championships and then won a place on the Australian team for the 1996 Summer Olympics in Atlanta where the men's team finished fourth overall and he finished 26th individually. He made the Australian team again for the 2000 Summer Olympics in Sydney where he finished 36th in the individual competition.Away from archery, Gray has a nursing degree.

At the 2008 Summer Olympics in Beijing Gray finished his ranking round with a total of 654 points. This gave him the 39th seed for the final competition bracket in which he faced Cheng Chu Sian in the first round. Cheng won the match with 109-101 and would eventually reach the quarter finals in which Bair Badënov was too strong.