A mikveh is not simply a bath but a pool built to precise halakhic specification, its water sourced at least in part from a natural, gravity fed source such as rainwater or a spring, called mayim chayim, living water, and connected in a fixed technical way to a separate collection pool beneath or beside the pool used for immersion itself, so that a mikveh cannot legally be created from municipal tap water alone however clean. Full body immersion in such a pool, with nothing between the body and the water, no jewellery, bandage or even nail polish that Jewish law treats as a chatzitzah, an interposition breaking the required direct contact, marks several distinct transitions in Jewish ritual status rather than serving as an act of physical hygiene.
The most widely observed use today is niddah, the monthly immersion married women perform after menstruation and a subsequent count of seven clean days, which permits the resumption of marital relations under traditional Jewish law; converts to Judaism immerse as the concluding legal act of conversion; and many observant men immerse before Yom Kippur, before their own wedding, or as a regular devotional practice, particularly within Hasidic communities, reflecting a use of the mikveh that extends well beyond its most statistically common application.