Irregular periods refer to menstrual cycles that vary significantly in length, timing, or flow from month to month. This can include cycles that are shorter or longer than normal, missed periods, unusually heavy or light bleeding, or bleeding between periods. Irregular menstruation can be caused by hormonal imbalances, stress, certain medications, underlying medical conditions such as polycystic ovary syndrome (PCOS), or changes in lifestyle. While occasional irregularity is common, persistent changes may require medical evaluation.