The Greyhound is a very old breed of dog, a sighthound which has been historically bred for coursing game and latterly Greyhound racing. Since the rise in large scale adoption of retired racing Greyhounds, particularly in North America from the end of the 20th century, it has seen a resurgence in popularity as a family pet.

According to Merriam-Webster, a Greyhound is "any of a breed of tall slender graceful smooth-coated dogs characterized by swiftness and keen sight...of several related dogs."

It is a gentle and intelligent breed whose combination of long, powerful legs, deep chest, flexible spine and slim build allows it to reach average race speeds in excess of 64 kilometres per hour (40 mph). The Greyhound can reach a full speed of 70 kilometres per hour (43 mph) within 30 metres or six strides from the boxes, traveling at almost 20 metres per second for the first 250 metres of a race. There are few mammals that can accelerate faster over a short distance, such as the cheetah, which can reach speeds of 109 kilometres per hour (68 mph) over 3-4 strides from a standing start, and pronghorn with an alleged top speed of 93 kilometres per hour (58 mph).

Temperament
The Greyhound is not an aggressive dog, as some may believe due to muzzles worn during racing. Muzzles are worn to prevent injuries resulting from dogs nipping one another during or immediately after a race, when the 'hare' has disappeared out of sight and the dogs are no longer racing but still excited. The thin skin of the Greyhound can tear easily from a small nick from teeth, so even a minor skirmish can result in stitches and time out from racing. Greyhounds with a high prey drive occasionally wear muzzles outside the racetrack; owners aware that their Greyhound has a high tendency to chase small prey will protect the prey by applying the muzzle.

Contrary to popular belief, adult Greyhounds do not need extended periods of daily exercise, as they are bred for sprinting rather than endurance. Greyhound puppies that have not been taught how to utilize their energy, however, can be hyperactive and destructive if not given an outlet, and they require more experienced handlers.

Greyhounds as pets
Greyhound owners and adoption groups consider Greyhounds to be wonderful pets.

Greyhounds are quiet, gentle, and loyal to owners. They are very loving creatures, and they enjoy the company of their humans and other dogs. Whether a Greyhound enjoys the company of other small animals or cats depends on the individual dog's personality. Greyhounds will typically chase small animals; those lacking a high 'prey drive' will be able to coexist happily with toy dog breeds and/or cats. Many owners describe their Greyhounds as "45-mile-per-hour couch potatoes".

Greyhounds live most happily as pets in quiet environments. They do well in families with children as long as the children are taught to treat the dog properly and with politeness and appropriate respect. Greyhounds have a sensitive nature, and gentle commands work best as training methods.

Greyhounds cope well as three-legged dogs.
Occasionally, a Greyhound may bark; however, Greyhounds are generally not barkers, which is beneficial in suburban environments, and they are usually as friendly to strangers as they are with their own family.

A very common misconception regarding Greyhounds is that they are hyperactive. In retired racing Greyhounds, this is usually not the case. Greyhounds can live comfortably as apartment dogs, as they do not require much space and sleep close to 18 hours per day. In fact, due to their calm temperament, Greyhounds can make better "apartment dogs" than smaller, more active breeds.

At most race tracks, Greyhounds are housed in crates for sleeping. Most such animals know no other way of life than to remain in a crate the majority of the day. Crate training a retired Greyhound in a home is therefore generally extremely easy.

Many Greyhound adoption groups recommend that owners keep their Greyhounds on a leash whenever outdoors, except in fully enclosed areas. This is due to their prey-drive, their speed, and the assertion that Greyhounds have no road sense. In some jurisdictions, it is illegal for Greyhounds to be allowed off-lead, even in off-lead dog parks, so it is important to be familiar with the relevant local laws and regulations. However, a good run at least once a week is important, especially for younger Greyhounds, and suitable areas can usually be found. Due to their size and strength, adoption groups recommend that fences be between 4 and 6 feet, to prevent them from jumping out.

Roles of the breed
Coursing
The original primary use of Greyhounds, both in the British Isles and on the Continent of Europe, was in the coursing of deer. Later, they specialized in competition hare coursing. Some Greyhounds today are still used for coursing, although artificial lure sports like lure coursing and racing are far more common and popular.

However, many breeders of racing Greyhounds argue that coursing is still important. This is the case particularly in Ireland, where many of the world’s leading breeders are based. A bloodline that has produced a champion on the live hare coursing field is often crossed with track lines in order to keep the early pace (e.g. speed over first 100 yards), which Greyhounds are renowned for, prominent in the line. Many of the leading sprinters over 300 yards to 550 yards have bloodlines traceable back through Irish sires within a few generations that won events such as the Irish Coursing Derby or the Irish Cup.

The majority of pure-bred Greyhounds are whelped in Ireland. Researching via Greyhound data websites will note coursing champions within a few generations in the pedigree of track racing champions.

Racing
Until the early twentieth century, Greyhounds were principally bred and trained for hunting and coursing. During the 1920s, modern Greyhound racing was introduced into the United States and England (Belle Vue Stadium, Manchester, July 1926), as well as Northern Ireland (Celtic Park (Belfast), April 1927) and the Republic of Ireland (Shelbourne Park, Dublin).[citation needed] Australia also has a significant racing culture. Aside from professional racing, many Greyhounds enjoy success on the amateur race track. Organizations like the Large Gazehound Racing Association (LGRA) and the National Oval Track Racing Association (NOTRA) provide opportunities for Greyhounds and other sighthound breeds to compete in amateur racing events all over the United States.

Companion
Historically, the Greyhound has, since its first appearance as a hunting type and breed, enjoyed a specific degree of fame and definition in Western literature, heraldry and art as the most elegant or noble companion and hunter of the canine world. In modern times, the professional racing industry with its large numbers of track bred Greyhounds, as well as the international adoption programs aimed at rescuing and re-homing dogs surplus to the industry, have redefined the breed in their almost mutually dependent pursuit of its welfare, as a sporting dog that will supply friendly companionship in its retirement. Outside the racing industry and coursing community, the Kennel Clubs' registered breed still enjoys a modest following as a show dog and pet. There is an emerging pattern visible in recent years (2009–2010) of a significant decline in track betting and multiple track closures in the US, which will have consequences for the origin of future companion Greyhounds and the re-homing of current ex-racers.

The breed's origin has in popular literature often romantically been connected to Ancient Egypt, in which it is believed "that the breed dates back about 4,000 years "a belief for which there is no scientific evidence. While similar in appearance to Saluki (Persian Greyhound) or Sloughi (tombs at Beni Hassan c. 2000 BCE), analyses of DNA reported in 2004 suggest that the Greyhound may not be closely related to these breeds, but is a close relative to herding dogs. Historical literature on the first sighthound in Europe (Arrian), the vertragus, the probable antecedent of the Greyhound, suggests that the origin is with the ancient Celts from Eastern Europe or Eurasia. Greyhound-type dogs of small, medium, and large size, would appear to have been bred across Europe since that time. All modern, pure-bred pedigree Greyhounds are derived from the Greyhound stock recorded and registered, firstly in the private 18th century, then public 19th century studbooks, which ultimately were registered with coursing, racing, and kennel club authorities of the United Kingdom.

Historically, these sighthounds were used primarily for hunting in the open where their keen eyesight is valuable. It is believed that they (or at least similarly named dogs) were introduced to the area now known as the United Kingdom in the 5th and 6th century BCE from Celtic mainland Europe although the Picts and other peoples of the northern area now known as Scotland were believed to have had large hounds similar to that of the deerhound before the 6th century BCE.

The name "Greyhound" is generally believed to come from the Old English grighund. "Hund" is the antecedent of the modern "hound", but the meaning of "grig" is undetermined, other than in reference to dogs in Old English and Old Norse. Its origin does not appear to have any common root with the modern word "grey" for color, and indeed the Greyhound is seen with a wide variety of coat colors. The lighter colors, patch-like markings and white appeared in the breed that was once ordinarily grey in color. The Greyhound is the only dog mentioned by name in the Bible; many versions, including the King James version, name the Greyhound as one of the "four things stately" in the Proverbs. However, some newer biblical translations, including The New International Version, have changed this to strutting rooster, which appears to be an alternative translation of the Hebrew term mothen zarzir. But also the Douay–Rheims Bible translation from the late 4th-century Latin Vulgate into English translates "a cock."

According to Pokorny the English name "Greyhound" does not mean "grey dog/hound", but simply "fair dog". Subsequent words have been derived from the Proto-Indo-European root *g'her- "shine, twinkle": English grey, Old High German gris "grey, old", Old Icelandic griss "piglet, pig", Old Icelandic gryja "to dawn", gryjandi "morning twilight", Old Irish grian "sun", Old Church Slavonic zorja "morning twilight, brightness". The common sense of these words is "to shine; bright".

In culture
The Greyhound is often used as a mascot by sports teams, both professional and amateur, as well as many college and high school teams.
Professional
Sault Ste. Marie Greyhounds (Ontario Hockey League)
Ohio Valley Greyhounds (United Indoor Football)
College
Assumption College (in Worcester, Massachusetts)
University of Indianapolis
Loyola University Maryland
Eastern New Mexico University
Moberly Area Community College (in Moberly, Missouri)
Moravian College in Bethlehem, Pennsylvania
Yankton College (Yankton, South Dakota)
Athol Murray College of Notre Dame (Wilcox, Saskatchewan)
Mid-South Community College (West Memphis, Ark.)
Fort Scott Community College (Fort Scott Kansas.)
Kearsney College (Botha's Hill, KwaZulu-Natal)
Foundation University (Dumaguete City, Negros Oriental, Philippines)
Other
Greyhound Bus Lines bus company occasionally airs television commercials starring a talking computer-generated Greyhound.
The Andhra Pradesh, (India) police force has a special ops unit named Greyhounds.
"Greyhound" was the name of several roller coasters in the United States and Canada. None of these rides operate today.
In Australia, racing Greyhounds are commonly known in slang terminology as "dish lickers" (e.g., "I just won 50 bucks at the dish lickers").
The Who's 1968 non-album singles "Dogs" and "Dogs (Part II)" are humorous references to Greyhound racing and the associated betting.
The main-character family of the animated television series The Simpsons have a Greyhound named Santa's Little Helper, a retired racing greyhound who was adopted by the family at the conclusion of the pilot episode.
1 Factory Radio, a car radio remanufacturer based out of Richmond, VA, prominently features a greyhound in their logo based on the real-life retired racer "mascots", Star Terrific and Bob's Logo.
The cover art of the 1994 Britpop album "Parklife" by Blur features Greyhounds.
The M8 Light Armored Car, a US military vehicle, was nicknamed "Greyhound" by British armed forces during the Second World War.
Kite, a character from the anime/manga series Ginga Densetsu Weed is supposedly a Greyhound mix.
In French, the sexual position known as doggy style is known as Position de la levrette (Position of the (female) Greyhound).