“Cattle” can only be used in the plural and not in the singular: it is a plurale tantum. Thus one may refer to “three cattle” or “some cattle”, but not “one cattle”. “One head of cattle” is a valid though periphrastic way to refer to one animal of indeterminate or unknown age and sex; otherwise no universally used single-word singular form of cattle exists in modern English, other than the sex- and age-specific terms such as cow, bull, steer and heifer. Historically, “ox” was not a sex-specific term for adult cattle, but generally this is now used only for working cattle, especially adult castrated males. The term is also incorporated into the names of other species, such as the musk ox and “grunting ox” (yak), and is used in some areas to describe certain cattle products such as ox-hide and oxtail.
See more at: Cow wash up buttercup poster