Insure, Ensure, Assure
To protect yourself against risk by regularly paying a special company that will provide a fixed amount of money if you are killed or injured or if your house or flat are damaged or stolen.
The house is insured for two million dollars.
They refused to insure us because they said we're too old.
To make something certain to happen.
The role of the police is to ensure that the law is obeyed.
Winning the lottery ensured his happiness.
To tell someone confidently that something is true, especially so that they do not worry (to remove doubt about, to guarantee).
"Don't worry, your motorbike will be ready tomorrow," the mechanic assured him.
The prime minister assured the electorate that taxes would not be increased after the election.
Insure, ensure & assure all mean "to make sure or certain of".
Hard work will insure/ensure/assure your success.