وَالطُّهْرُ إِذَا تَخَلَّلَ بَيْنَ الدَّمَيْنِ فِي مُدَّةِ الْحَيْضِ، فَهُوَ كَالدَّمِ الْجَارِي.
Meaning: If a period of purity intervenes between two bleedings within the menstrual span, it is treated like continuous bleeding.
Tuhr mutakhallil is a clean interval between two episodes of bleeding. Its legal classification may depend on the overall duration and whether bleeding returns within the allowable menstrual period.
The broad statement is qualified in particular patterns by differing juristic methods.