assure
verbUK /əˈʃɔː/
US /əˈʃʊr/
To tell someone something is true so they stop worrying.
She assured her little brother that the dark was nothing to fear.
OTHER MEANINGS
2. To make something certain to happen.
Hard work assured his success in the contest.
3. To make someone feel sure about something.
The doctor assured us that the medicine was safe.
4. To state something firmly and with confidence.
He assured everyone that the plan would work.