If it lives on a farm, makes a mooing sound, and produces milk, it is probably a cow.
Most people would immediately identify a cow, the large, cud-chewing female of what is known as "cattle." Cows are typically domesticated farm animals, though the females of wilder bovine relatives are also called cows. The verb form of cow, "to frighten or subdue," comes from the docile nature of most cows — they are fairly easy to intimidate, or easily cowed. The Old English root is cu, from the Indo-European gwous, which might have developed from the sound that cows make.