The Sanskrit word Kula means family, clan, or in-group. It also has a second, more occult meaning: the sacred place where the lone Nath or the clan enters the Sanctum. That concept can be defined as absorption into the field of Divine Shakti—a spiritual crossroads of the living and the ethereal.
Within the International Nath Order, Kula is the company and the ground, not the name of the tantric sect. Sri Kapilnath writes of it as the place where the spirits of living Naths commune with the departed Nath Siddhas of the lineage. The working form of that circle is the zonule (also called kula chakra). One enters the wider in-group by initiation or by friendly association; the Sanctum itself is entered by alignment and work. Do not read Kula as another word for Kaula. Kaula is the way of life and the historical stream. Kula is the clan-circle in which that way is kept.