Everyone knows what a cow is, right? But did you know that they're not actually called "cows"? The term is purely colloquial, and not the proper term for the species at all.
You may have seen the news going around recently about a giant cow named Knickers who, with his mammoth size, has quickly become Australia's favourite cow. Only, because this is the internet and no one can just enjoy something fun, you may have seen a few pedantic commenters pointing out that Knickers is not, in fact, a cow. So what is he, then?
The species most people would refer to as a cow is actually correctly called "cattle". Yup that's the name of the animal. However like with other farm animals, there are a whole lot of specific naming conventions for different types of cattle. So a cow isn't actually everything that moos: technically it only refers to the females, and even more specifically females who have had a calf.
The males are called bulls, though castrated males are often called steers - which is what Knickers is if you want to be most correct. Another common term, heifer, is used for young females before they have calved.
As though that's not confusing enough, there's a whole heap of other terms that vary based on the region and the type of farming being done. One of the biggest divergent names is the ox: referring to cattle that are used for riding, ploughing or as a draught animal. In Australia and a few other regions, oxen are more commonly referred to as bullocks.
Congratulations, you're now armed with at least a partial knowledge of cattle etymology: But that doesn't mean you're allowed to be a pedant about it. Everyone knows what a cow is, so let's just call it that.