Is menstruation considered menses (hayd)? How does a man know that it has begun? Is it permissible for a husband to have intercourse with his wife during it with the intention of procreation?

The term "menstrual cycle" is applied to the combined periods of purity (non-menstruation) and menstruation, or to the period of menstruation alone. A man knows the beginning and end of it by asking his wife. It is not permissible for a man to have intercourse with his wife during her menstrual period, but it is permissible for him to do so at any time after its conclusion and her purification.