Is it ensure, insure, or assure?
early 15c., "derived by interpretation," from Middle French constructif or from Medieval Latin constructivus, from Latin construct-, past participle stem of construere "to heap up" (see construction). Meaning "pertaining to construction" is from 1817; "having the quality of constructing" is from 1841. Related: Constructively. Constructive criticism is attested by 1841.