For domestic cattle, a young ox is a calf or a steer, sometimes called a working steer. In the case of musk oxen or other wild oxen, a young ox is a calf, a heifer or, occasionally, a stot.
The domestic animal referred to as an ox is actually a domestic bull or cow that is used as a draft animal. Usually, the ox is a male that has been castrated, resulting in a draft animal that is large but docile. These animals are nearly always referred to as steers when they are young and bullocks when they are older.
In the wild, a young male ox is generally called a calf. A young female who has not yet given birth is a heifer.