assurance
This term conveys a sense of certainty and security, whether it is an external promise made to another person or an internal state of confidence. It differs from a simple promise by implying a stronger, more formal commitment designed to eliminate anxiety or doubt. In British English, the word is used specifically in a financial context to describe a life insurance policy that is guaranteed to pay out, as opposed to insurance which only pays if a specific event occurs. This creates a distinct semantic divide between the general sense of confidence and the technical legal sense of a guaranteed payout.
Meanings
A positive declaration intended to give confidence or to remove doubt.
"He gave me his assurance that the project would be finished on time."
Confidence in one's own abilities or character.
"Her self-assurance during the presentation impressed the board of directors."