Which condition is characterized by bleeding between menstrual periods?

The condition characterized by bleeding between menstrual periods is metrorrhagia. This term specifically refers to irregular menstrual bleeding that occurs at times other than the expected menstrual cycle. Metrorrhagia can be indicative of a variety of underlying issues, which might include hormonal imbalances, uterine fibroids, or other gynecological conditions.

In contrast, polymenorrhea describes a condition where a woman experiences menstrual cycles that are shorter than the typical 21-35 day range, leading to more frequent periods. Menorrhagia refers to abnormally heavy or prolonged menstrual bleeding during a regular menstrual cycle, which is distinct from the intermittent bleeding described in metrorrhagia. Amenorrhea, on the other hand, is the absence of menstruation altogether, which does not apply to the scenario of bleeding occurring between cycles. Thus, the definition and implications of metrorrhagia make it the correct choice for this question.