While Yoga may be in Religions, the many Yoga practices with body, breath and mind, along with their transcendent goal of direct experience, are generally neither characteristic of Religions, nor typically practiced by the adherents of Religions.
Yoga is contained within religions. Religion is not contained within Yoga.
Yoga means union. It is the joining together the aspects of ourselves which were never divided in the first place. To say that the word Yoga itself is a religion makes as much sense as saying that the words Union or Holistic are themselves religions.