assure, ensure, insure

Assure is used in the sense of offering a guarantee or removing doubt, uncertainty or worry.

• Thanks to the new regulations, the employees’ job security was assured.
• The builder assured the homeowner that the renovations would be completed on time.

Ensure means to make sure or certain.

• To ensure that he could keep his word, the builder hired two extra carpenters.

Insure is related primarily to the field of insurance, and sometimes to preparing for the future.

• If you insure your life, you assure your family members a settlement and ensure their financial security.
• Insure (or Ensure) your future by continuing your education.