Ouch! Unca Dave O, you got me! Beat the drums slowly, etc. I always thought that those big, 4-square beasts called oxen and hauling parade wagons and pulling sledges were a sort of selected breed of cattle. Turns out that most of them are just old steers, having lost their manhood some three years or more after they were born. There are a couple of farms here where the owner has selected for a few generations, not castrating likely bulls which he wishes to breed with likely females in order to get better draft animals, but this is apparently a modern twist by hobbyists.
I looked up a bunch of stuff, and it turns out to be quite a can of rocky mountain oysters.

Getting into the various meanings of ox is beyond the purpose of most dictionaries, but-
Starting at the beginning, ox, oxen, was the Saxon name for the males of domesticated cattle. To a zoologist, however, the term includes bovine animals of every description- true oxen, bison and buffalos.
The Bovidae are those bovines typified by horns which are never branched. The subfamily Bovinae includes the ox tribe and a couple of African groups- duikers and bushbucks. Narrowing down, the Tribe Bovini harbors the ox, buffalo, bison, etc.

Sticking to the domesticated cattle of the type we know.
Terminology- sex, etc.
The male is first a "bull-calf." If left alone, it becomes a bull, but if it is castrated, it becomes a "steer," and in 2-3 years grows to become an "ox."
The female is first a heifer-calf, growing into a heifer, and after 2-3 years becomes a "cow." Heifers may be spayed ("spayed heifer").
Working bulls are generally emasculated to quiet them down- "working oxen."

Now if I can only remember this when the next thread on the subject comes up-