Cow

Cows or more aptly called Cattle, are large mammals mentioned briefly in the How to Train Your Dragon Book series.

Description
Cattle are large bovine mammals, almost always referring to the domesticated Bos taurus. To note, "Cattle" is a more appropriate, albeit plural term. No singular term exists. The term "cow" or plural "cows" is commonly used, but is also more specifically used to refer to an adult female.

Cattle are ruminants and even-toed ungulates, meaning they have four 'stomachs' for specialized digestion of grasses and other plant matter, and walk on two hooved toes. They are social animals and arrange themselves into hierarchical groupings, or herds. Domesticated cattle come in many different breeds, with different body structures, colors, horns or polled, and coat types. Body structure is heavily influenced by their purpose for humans.

Function
Cattle are used primarily for meat production or milk production. However, many parts of the cow can be used for other products, such as the hide for leather or the horns for a variety of tools and objects.

In the Book series, cattle are mentioned as a descriptor for something else or as a food item.

How to Be a Pirate
Cows are mentioned once in Book 2; more specifically a 'bull'. Bulls are a term used for an adult, intact male.

"Stoick was a terrifying red-headed bull of a man whose belly turned a corner a good foot or two before the rest of him."

- Book 2

How to Speak Dragonese
Cattle are mentioned as a food item on the menu for the Fat Consul - "Whole roast ox marinated in pickled slitherhawk and shark's eyeballs".

Ox is a term most often used to refer to adult cattle used for draft purposes. These animals are most often castrated males.