assure

A transitive verb that means to make sure or certain or convince; to inform positively; to make certain the coming or attainment of or guarantee; to make safe (as from risks or against overthrow); or to give confidence to.
glancing back to assure himself no one was following

Examples:

• I assure you that we can do it.
• EAPM works hard to assure our donors that their funding is being put to good use.
• The military assured the commander the security of the base.

Do not confuse with insure or ensure.