Absence or cessation Amenorrhea: Absence or cessation of menstruation. Amenorrhea isconventionally divided into primary and secondary amenorrhea.Primary amenorrhea -- menstruation never takes place. It fails to occur at puberty.Secondary amenorrhea -- menstruation starts but then stops. The absenceof menstruation during pregnancy is a form of physiologic secondary amenorrhea,physiologic in the sense that it is completely normal and is not caused byanything medically harmful (pathologic). Amenorrhea during lactation isanother type of physiologic secondary amenorrhea. The word "amenorrhea" is compoundedfrom three Greek roots "a-", no + "men", month + "rhoia", flow = no monthlyflow. Amenorrhea is less commonly called amenia.