What does 'rest' mean in 'rest assured' and where else 'rest' can be used in this way? What is the different between it and 'to be assured'?

You may rest assured of that.

  • “rest” as a verb, and “assured (of that)” as a past participle clause, forming the idiom “to rest assured.” Commented May 13, 2021 at 9:30

2 Answers 2


"Rest assured" is an idiomatic expression similar to "sleep well". When you have trouble on your mind, you sleep poorly, but if that trouble is resolved, you can have a restful sleep.

In the same way, "rest assured" figuratively means that when you next lie down to take a rest you can feel comfortable knowing that some issue will not be a problem.

You can rest assured that you will never again be baffled by the idiomatic expression "rest assured".

(Edit). The verb "rest" actually comes from two different languages trees (Old English/German and French/Latin). An alternate (and somewhat archaic) meaning of "rest" is "remain" from the French rester. It may be that "rest assured" actually means to "remain/stay/be assured" rather than "sleep assured".

Either way, this does not really change the meaning or usage of the phrase, but it is interesting to consider. Also it helps explain why there is little (if any) semantic difference between "rest assured" and "be assured". Because "rest assured" feels like a guarantee or a blessing, in some contexts it may sound better.

  • Undoubtedly, the meaning of rest assured is be at ease, but this answer seems to suggest that the meaning of rest is metaphorical. Are you sure it's not simply an archaic use of rest to mean remain as in the French rester? In this example, it's hard to tell, because the metaphorical use of rest seems possible. But there are other examples where rest more obviously meant remain. For example, "God rest ye merry, gentlemen" which was a supplication to God to keep you merry, not that He should let merry gentlemen relax.
    – Juhasz
    Commented Mar 5, 2019 at 16:58
  • @Juhasz It's certainly possible. I'll add that alternate explanation.
    – Andrew
    Commented Mar 5, 2019 at 17:22
  • @Juhasz Thank you for your comment, which makes the downvote I received less justifiable.
    – Gustavson
    Commented Mar 5, 2019 at 20:08
  • 1
    @Andrew You forgot to explain the difference between "rest assured" and "be assured", as requested by OP.
    – Gustavson
    Commented Mar 5, 2019 at 20:31
  • For what it's worth @Gustavson, I don't see anything wrong with your answer. I think that some users believe the are supposed to vote down on an answer they disagree with. This is, of course, not correct and not constructive.
    – Juhasz
    Commented Mar 5, 2019 at 21:33

"rest assured" is formal and is used to calm somebody down so that they will not worry. It is usually used in the imperative or with "can". "rest" is close in meaning to "remain" or "stay":

  • Rest assured that this is the best for you.
  • You can rest assured that this is the best for you.

The Oxford English Dictionary states that the meaning of "rest" in this phrase is "remain".

Below is a transcription of OED entry 3 for "rest":

rest: 3 remain or be left in a particular condition: rest assured.

"be assured" is used to express that the subject will obtain something for sure. Here follow some examples from the Longman dictionary:

• People do work without the institutional system of capitalism and they are assured of a reasonable livelihood.

• The team is assured of a spot in the finals.

• There was no reason for a playoff game because both were assured of advancing to the postseason.

• Cooke was a happier man when greeting the news that full-back Jon Webb is assured of completing the season.

• When he did, he was assured of immediate payment.

• Residents must be assured of their physical security before any region can grow.

• Only three of them secured enough votes to be assured of their seats.

  • Downvoters are kindly invited to explain why they have penalized me.
    – Gustavson
    Commented Mar 5, 2019 at 21:01

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