ensure

[c.1385, from Anglo-Fr. 'enseurer', from 'en-' make + O.Fr. 'seur' sure probably infl. by O.Fr. 'asseurer' assure]

v.
1. To make certain of.

2. To be careful or certain to do something; to make certain of something.

3. To betroth.

4. Insure.