Is it ensure, insure, or assure?
reinforcement re·in·force·ment (rē'ĭn-fôrs'mənt)
The act or process of reinforcing.
Something that reinforces.
The occurrence or experimental introduction of an unconditioned stimulus along with a conditioned stimulus.
The strengthening of a conditioned response by such means.
An event, a circumstance, or a condition that increases the likelihood that a given response will recur in a situation like that in which the reinforcing condition originally occurred.