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Cattle (colloquially cows) are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius. Cattle are raised as livestock for meat (beef and veal), as dairy animals for milk and other dairy products, and as draft animals (oxen or bullocks) (pulling carts, plows and the like). Other products include leather and dung for manure or fuel. In some countries, such as India, cattle are sacred. From as few as 80 progenitors domesticated in southeast Turkey about 10,500 years ago, an estimated 1.3 billion cattle are in the world today. In 2009, cattle became the first livestock animal to have a fully mapped genome.

Bos (from Latin bōs: cow, ox, bull) is the genus of wild and domestic cattle. Bos can be divided into four subgenera: Bos, Bibos, Novibos, and Poephagus, but these divisions are controversial. The genus has five extant species. However, this may rise to seven if the domesticated varieties are counted as separate species, and nine if the closely related genus Bison is also included. Modern species of cattle are believed to have originated from the extinct aurochs.

A bovid (family Bovidae) is any of almost 140 species of cloven-hoofed, ruminant mammals with characteristic unbranching horns covered in a permanent sheath of keratin in at least the males.

The family is widespread, being native to Asia, Africa, Europe and North America, and diverse: members include bison, African buffalo, water buffalo, antelopes, gazelles, sheep, goats, muskoxen, and domestic cattle.

The Pecora are a group of hoofed mammals that comprise most of the ruminants, including cattle, sheep, goats, antelopes, deer, giraffes, and pronghorns. The only extant members of the Ruminantia that are not pecorans are the chevrotains, which lack horns and whose four-chambered stomachs are less developed than those of the pecorans. This gives rise to the pecorans sometimes being called "horned ruminants". Pecorans are also known as "higher ruminants", because they arose more recently than other ruminant groups. Although Pecora is well-supported as a clade, the exact relationships among families within it are in dispute.

Flower, W.H. (1883). "On the arrangement of the orders and families of existing Mammalia". Proceedings of the Zoological Society of London 1883: 178–186. 

Hassanin, Alexandre, & Douzery, Emmanuel J. P. (2003). "Molecular and morphological phylogenies of Ruminantia and the alternative position of the Moschidae". Systematic Biology 52 (2): 206–228. doi:10.1080/10635150390192726. PMID 12746147. 

Ruminantia includes many of the well-known large grazing or browsing mammals: among them cattle, goats, sheep, deer, and antelope. All members of the Ruminantia are ruminants: they digest food in two steps, chewing and swallowing in the normal way to begin with, and then regurgitating the semi-digested cud to re-chew it and thus extract the maximum possible food value.

Not all ruminants belong to the Ruminantia. Camels and llamas are among the exceptions, a suborder known as Tylopoda. Also, there are a number of other large grazing mammals that, while not strictly ruminants, have similar adaptations for surviving on large quantities of low-grade food. Kangaroos and horses are examples.

The Tragulidae are the basal family in the Ruminantia.

The ancestral Ruminantia karyotype is 2n = 48 similar to that of cetartiodactyls.

The even-toed ungulates (Artiodactyla) are ungulates (hoofed animals) whose weight is borne about equally by the third and fourth toes, rather than mostly or entirely by the third as in odd-toed ungulates (perissodactyls), such as horses.

Artiodactyla comes from (Greek: ἄρτιος (ártios), "even", and δάκτυλος (dáktylos), "finger/toe"), so the name "even-toed" is a translation of the description. This group includes pigs, peccaries, hippopotamuses, camels, llamas, chevrotains (mouse deer), deer, giraffes, pronghorn, antelopes, sheep, goats, and cattle. The group excludes whales (Cetacea) even though DNA sequence data indicate that they share a common ancestor, making the group paraphyletic. The phylogenetically accurate group is Cetartiodactyla (from Cetacea + Artiodactyla) .

There are about 220 artiodactyl species, including many that are of great nutritional, economic, and cultural importance to humans.

A further distinguishing feature of the group is the shape of the astragalus (talus), a bone in the ankle joint, which has a double-pulley structure. This gives the foot greater flexibility.