Even if these words all have something to do with being sure, they are easily confused.
- Assure means to tell someone that something will happen or that something is definitely true.
My doctor has assured me that I will be able to read without glasses after my surgery.
- To reassure somebody means to make them feel less worried or frightened about a problem.
They reassured us that they would look into the matter.
- Ensure means to make sure that something will (or will not) happen.
Please ensure that all windows are closed and all doors are locked before you leave the building.
- Insure means to buy insurance to protect against something bad happening to you or your possessions.
You’d better insure your gear before you go hiking in the mountains.