Is it ensure, insure, or assure?
late 15c., "of or pertaining to a whole," from Middle French intégral (14c.), from Medieval Latin integralis "forming a whole," from Latin integer "whole" (see integer). Related: Integrally. As a noun, 1610s, from the adjective.
Adjective Involving or expressed as an integer or integers.
Noun See definite integral, indefinite integral.