menorrhea
The absence of a menstrual period.
only people have a menstrual cycle but mammals have something called Estrous cycle and there is sometimes bloody discharge. fish are not mammals and they don't have it.
The endometrial lining.
Yes, you can feel menstrual flow leaving your body. It's just the same as with discharge, you can feel the fluid leaving your body - menstrual flow is often heavier and warmer than discharge.
The discharge probably means you will get your period soon. A friend of mine also told me that discharge cleans out the vagina.
Yes.
Yes, a period is a real thing. In biology, it refers to the monthly discharge of blood and tissues from the uterus that occurs in the absence of pregnancy. Periods are a normal part of the menstrual cycle for females of reproductive age.
Yes.
Amenorrhea
condition of the inner lining of the uterus
that is puberty