Is it ensure, insure, or assure?
early 14c., from Latin ritus "religious observance or ceremony, custom, usage," perhaps from PIE root *re(i)- "to count, number" (cf. Greek arithmos "number," Old English rim "number;" see read (v.)). Rite of passage (1909) is translated from French rite de passage, coined by French anthropologist Arnold van Gennep (1873-1957).
the performance of ceremonial acts prescribed by tradition or by sacerdotal decree. Ritual is a specific, observable mode of behaviour exhibited by all known societies. It is thus possible to view ritual as a way of defining or describing humans.