A male chicken is a cock or a cockerel, depending on its age. Similarly, a female chicken is called a pullet or a hen.
The age at which a pullet becomes a hen and a cockerel becomes a cock depends on what type of chicken is being raised.
Purebred poultry producers have very age-specific definitions. A chicken is a cockerel or pullet if it is less than one year of age.
After one year of age, the chicken is referred to as a hen or cock. A sexually mature male chicken (around five months of age) is referred to as a rooster.