Is it ensure, insure, or assure?
in anthropology, the process by which a cultural trait, material object, idea, or behavior pattern is spread from one society to another; also called diffusion
diffusion dif·fu·sion (dĭ-fyōō'zhən)
The process of diffusing or the condition of being diffused.
The spontaneous intermingling of the particles of two or more substances as a result of random thermal motion.