A sheep in its first year is a lamb and its meat is also lamb. A sheep in its second year and its meat are hogget. Older sheep meat is mutton. Generally, "hogget" and "sheep meat" are not used by consumers outside New Zealand, South Africa and Australia with the exception of the Navajo people in the American Southwest, who consume mutton as a staple part of their diet. Historically, Navajo sheep ranching has been regulated by the Federal Government due to habitat destruction caused by sheep overgrazing. 
Lamb is the most expensive of the three types and in recent decades sheep meat is increasingly only retailed as "lamb", sometimes stretching the accepted distinctions given above. The stronger-tasting mutton is now hard to find in many areas, despite the efforts of the Mutton Renaissance Campaign in the UK. In Australia, the term prime lamb is often used to refer to lambs raised for meat. Other languages, for example French, Spanish, Italian and Arabic, make similar or even more detailed, distinctions among sheep meats by age and sometimes by sex and diet, though these languages do not always use different words to refer to the animal and its meat -- for example, lechazo in Spanish refers to meat from milk-fed (unweaned) lambs.
The definitions for lamb, hogget and mutton vary considerably between countries. Younger lambs are smaller and more tender. Mutton is meat from a sheep over two years old, and has less tender flesh. In general, the darker the colour, the older the animal.
In the early 1900s, mutton was widely consumed in the United States, but mutton consumption has declined since World War II. As of 2010 , most sheep meat in the United States comes from animals in between 12 and 14 months old, and is called "lamb"; the term "hogget" is not used. Federal statutes and regulations dealing with food labeling in the United States permit all sheep products to be marketed as "lamb."USDA grades for lamb are only partly a function of the animal's age. Animals up to 20 months old may meet the quality of the "USDA prime" grade depending on other factors, while "USDA choice" lamb can be of any age. "Spring lamb" is defined by the USDA as having been slaughtered between March and October.
The term "mutton" is applied to goat meat in most of these countries, and the goat population has been rising. For example, mutton-curry is always made from goat meat. It is estimated that over one-third of the goat population is slaughtered every year and sold as mutton. The husbanded sheep population in India and the Indian subcontinent has been in decline for over 40 years and has survived at marginal levels in mountainous regions, based on wild-sheep breeds, and mainly for wool production.
The meat of a lamb is taken from the animal between one month and one year old, with a carcass weight of between 5.5 and 30 kg (12 and 66 lb). This meat generally is more tender than that from older sheep and appears more often on tables in some Western countries. Hogget and mutton have a stronger flavour than lamb because they contain a higher concentration of species-characteristic fatty acids and are preferred by some. Mutton and hogget also tend to be tougher than lamb (because of connective tissue maturation) and are therefore better suited to casserole-style cooking, as in Lancashire hotpot, for example.
Lamb is often sorted into three kinds of meat: forequarter, loin, and hindquarter. The forequarter includes the neck, shoulder, front legs, and the ribs up to the shoulder blade. The hindquarter includes the rear legs and hip. The loin includes the ribs between the two.
Lamb chops are cut from the rib, loin, and shoulder areas. The rib chops include a rib bone; the loin chops include only a chine bone. Shoulder chops are usually considered inferior to loin chops; both kinds of chops are usually grilled. Breast of lamb (baby chops) can be cooked in an oven.
Forequarter meat of sheep, as of other mammals, includes more connective tissue than some other cuts, and, if not from a young lamb, is best cooked slowly using either a moist method, such as braising or stewing, or by slow roasting or American barbecuing. It is, in some countries, sold already chopped or diced.
Lamb shank definitions vary, but generally include:
Mutton barbeque is a tradition in Western Kentucky. The area was strong in the wool trade, which gave them plenty of older sheep that needed to be put to use.
Thin strips of fatty mutton can be cut into a substitute for bacon called macon.
Lamb tongue is popular in Middle Eastern cuisine both as a cold cut and in preparations like stews.
Approximate zones of the usual UK cuts of lamb:
According to the OECD-FAO Agricultural Outlook for 2016, the top consumers of sheep meat in 2015 were as follows: EU countries are not individually surveyed in this list. Among EU nations, Greece is the per capita leader in consumption at 12.3 kg, while the UK's annual per capita lamb consumption is 4.7 kg. Outside of the OECD, the largest per capita consumer overall is Mongolia, with 45.1 kg.
The table below gives a sample of producing nations, but many other significant producers in the 50-120 KT range are not given.
Source: Helgi Library, World Bank, FAOSTAT
Meat from sheep features prominently in the cuisines of several Mediterranean cultures including Greece, Turkey, North Africa, Jordan, and the Middle East, as well as in the cuisines of Pakistan and Afghanistan. In Greece for example, it is an integral component of many meals and of religious feasts such as Easter (see avgolemono, magiritsa). It is also very popular in the Basque culture, both in the Basque country of Europe and in the shepherding areas of the Western United States. In the United States, the Navajo have incorporated mutton and lamb into their traditional cuisine since the introduction of sheep by Spanish explorers and settlers in the 17th century, replacing wild turkey and venison and creating a pastoral culture. In Northern Europe, mutton and lamb feature in many traditional dishes, including those of Iceland, Norway and of the United Kingdom, particularly in the western and northern uplands, Scotland and Wales. Mutton used to be an important part of Hungarian cuisine due to strong pastoral traditions but began to be increasingly looked down on with the spread of urbanisation. It is also very popular in Australia. Lamb and mutton are very popular in Central Asia and in certain parts of China, where other red meats may be eschewed for religious or economic reasons. Barbecued mutton is also a specialty in some areas of the United States (chiefly Owensboro, Kentucky) and Canada. However, meat from sheep is generally consumed far less in the US than in many European, Central American and Asian cuisines; for example, average per-capita consumption of lamb in the United States is only 400 grams (14 oz) per year.
In Australia, the leg of lamb roast is considered to be the national dish. Commonly served on a Sunday or any other special occasion, it can be done in a kettle BBQ or a conventional oven. Typical preparation involves covering the leg of lamb with butter, pushing rosemary sprigs into incisions cut in the leg, and sprinkling rosemary leaves on top. The lamb is then roasted for two hours at 180 °C (350 °F) and typically served with carrots and potato (also roasted), green vegetables and gravy.
In Indonesia, lamb is popularly served as lamb satay and lamb curry. Both dishes are cooked with various spices from the islands, and served with either rice or lontong. A version of lamb and bamboo shoot curry is the specialty of Minang cuisine, although similar dish could also be found in Thai cuisine.
In Japan, although lamb is not traditionally consumed in most of the country, on the Northern island of Hokkaido and North-eastern Tohoku regions, a hot pot dish called Jingisukan (i.e. "Genghis Khan") is popular. In that dish, thin-sliced lamb is cooked over a convex skillet alongside various vegetables and mushrooms in front of the diners, then dipped in soy-sauce based dipping sauces and eaten. It was so named because lamb is popular in Mongolia (see "Sheep meat consumption" above).
Lamb's liver, known as lamb's fry in New Zealand and Australia, is eaten in many countries. It is the most common form of offal eaten in the UK, traditionally used in the family favourite (and pub grub staple) of liver with onions and/or bacon and mashed potatoes. It is a major ingredient, along with the lungs and heart (the pluck), in the traditional Scottish dish of haggis.
Lamb testicles or lamb fries are a delicacy in many parts of the world.
Lamb kidneys are found in many cuisines across Europe and the Middle East, often split into two halves and grilled (on kebabs in the Middle East), or sautéed in a sauce. They are generally the most highly regarded of all kidneys.