FYI.....semantics, maybe, but can be important communication terms when discussing chicken behavior.
Female chickens are called pullets until one year of age, then they are called hens.
Male chickens are called cockerels until one year of age, then they are called cocks(or cockbirds or roosters).
Age in weeks or months is always a good thing to note.
You have the technical definition, a female chicken less than a year old. In some circumstances that can be good to know, but as far as behaviors go age in weeks or months can be more important. Whether they are laying or not is even more important to me. Until they start laying they pretty much act like chicks or immature adolescents. When they start laying they take on more mature behaviors. I do not expect any change in behaviors when they turn one year old, they have been adults for a while. I do expect a change in behavior when they start to lay.