The term "cow" is only used for female cattle. Male, or boy, cattle are called bulls or steers. When born, a male is referred to as a "bull calf." If the bull calf is not castrated, it grows into a bull.
However, if the male is castrated, he is called a "steer" as an adult. Males are castrated to make them more manageable. A young female is a "heifer calf." As a heifer calf ages, it is simply called a "heifer." A fully adult female is a "cow."
The weights of bulls or cows depend upon their breeds. Typically, a bull weighs between 1,000 and 4,000 pounds. Cows usually tip the scale at 800 to 2,400 pounds.