I was watching a movie the other day and one character said to another, "Don't let's fight" instead of "Let's not fight." Is this proper usage, and if so, what is the grammatical rule that applies here?

  • 2
    Canonical example (from Alice in Wonderland): “Mustard! Now don’t let’s be silly!”
    – Jon Purdy
    Mar 1 '12 at 23:00
  • 6
    The answers here are fascinating. Before having seen this question and the answers below I would never have imagined that "Don't let's" would be anything other than a gross error made by a non-native speaker.
    – nohat
    Mar 2 '12 at 7:16
  • @BenLee: You are quoting very selectively. From your own link: "Let's not" is 118 times commoner than "let's don't" on Google, 95 times commoner on Yahoo, 98 times commoner on MSN. In news-oriented indices, the ratios tend to be larger.... And: That's a ratio of 304 in Google News, 169 in Yahoo News, and 41,438 in MSN News (where something strange is going on in this case). 3 of the 10 "let's don't" examples from Google News are Bush quotes; the other 7 are from NC, LA, TX, AL (2), LA(2) -- that's not just fly-over country, it's more specifically the American south. Mar 6 '12 at 3:09
  • @BenLee: I did not mean to accuse you of having a hidden agenda; perhaps I should have phrased it differently. I was just wondering why you quoted just that line, which suggests something quite different from the point of the article you linked to. The article is trying to show how that line is "missing a nuance", probably a euphemism for off the mark or misleading. Mar 6 '12 at 4:31

Michael Swan's book "Practical English Usage" has this to say:

There are two possible negatives, with let us not and do not let us (informal let's not and don't let's)

Let us not despair. (formal)

Let's not get angry. (informal)

Do not let us forget those who came before us. (formal)

Don't let's stay up too late tonight. (informal)

Forms with don't let's (and let's don't in American English) are very informal.

  • 4
    In American English, they are not informal at all, they just are not allowed. The forms are purely British. Don't confuse "informal" with "unproducable". The reason is that "Do not let us" (which is allowed) has, in American, a subject of the command "Do not let us" which is an actual subject, not the implicit non-subject that is doing the letting in "let's". This is explained in my answer. The "don't let's" is not informal--- it really means something different, which is unique to British English.
    – Ron Maimon
    Mar 2 '12 at 5:22
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    @RonMaimon You appear to be using a prescriptive instead of a descriptive grammar. "Don't let's" has some fairly wide usage amongst native American speakers, although the majority of use I've personally heard is from those under 30.
    – user14070
    Mar 2 '12 at 14:19
  • 1
    It's weird to me to see "Let's" described as "informal." I'd say it's neutral.
    – herisson
    Sep 1 '15 at 5:18

"Don't let's" wins before 1930...

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  • Notice that most "don't let's" from your results are in quotation marks: many appear to be part of an artificial rendering of informal speech in novels, alongside "ain't". The "let's not" appear more often in serious articles and dialogues. Mar 6 '12 at 3:17
  • These statistics ignore the ambiguity of the us component of let's [verb]: Does it include the addressee and thus function as an invitation, or does it exclude the addressee and thus function as a request for permission? Mar 6 '12 at 19:26

Contractions are not always grammatical just because their expanded forms are. The issue of the grammaticalness of contractions is determined by the rules of forming contractions, and their required context, and required subjects, objects and relations. These rules are not apparent just by writing down the expanded forms. The contraction "let's" is very specific, and is not just short for "let us".

For example:

  • "Mom let us go to the movies." (Mom gave us permission)
  • "Mom let's go to the movies."

The second is not a contraction of the first. Without a break between the "Mom" and the rest, it is ungrammatical and meaningless. The essential issue is that the "let" in "let's" must always be a command. But consider now the commands:

  • "Mom! Let us go to the movies!" (command for permission)
  • "Mom! Let's go to the movies!"

You see that the meaning is different. For non-native speakers, the second is saying that Mom should go to the movies with us, the first is (usually) commanding mom's permission.

In principle, the first can be a long form of the second, but only in certain formal contexts where contractions are disallowed. But the second form can never mean that the command is directed at mom. Let's just is not allowed to command a person like that. The "let" in "let's" always has as a subject, not a person, but a non-entity, similar to providence, or the French "on".

So you get "Mom! (Oh, providence,) let us go the movies!" as the best non-contracted approximation to "Mom! Let's go to the movies!", while the permission meaning doesn't allow the contraction, although it is the same meaning of "let", just with a different implicit subject.

In the case of "Don't let's fight", all these rules for the let's construction are fulfilled. So it is ok by these criteria.

  • "Mom! Don't let's go to the movies"
  • "Mon! Don't let us go the movies"

has the same difference in meaning as the first pair. So this is an ok construction, it really is grammatical to say "Don't lets" according to the explicit let-us contraction rules.

American vs. British English

The real difference here is in the different unspoken rules of implicit subjects for "let's" in British and American English. When there is a "don't", the "don't" has a verb "do" there which is also commanding of providence. So if you can say:

  • "Do let us go to the movies"
  • "Do let's go to the movies"

When the implicit subject of the command is providence, then you can say "don't let's". If you can't say "Do" with an implicit subject providence, you're cooked.

The do business is a pure British construction, which is un-American. In American, the implicit subject providence can "let" things, but it can't "do" things.

So American English allows:

  • "(Providence!) let us not go to the movies"
  • "let's not go to the movies"

But in American, when you say

  • "Do not let us go to the movies!"

There is a real subject, not providence, not a neutral subject. If there is no one who is obviously being adressed, it actually sounds like a prayer, because you fill in the subject as God. This is different than "Let's go!" which hardly ever sounds like a prayer, becuase the subject is the implicit neutral providence thing (I am sure that linguists have a name for this). In british, "don't let us go to the movies" obviously isn't a prayer. It has the same neutral providence subject as "let's go to the movies."

So when an American says:

  • "Don't let us go the movies!"

There is an implicit actual subject who is letting, like mom, or God, it isn't the neutral On-like providence. So the contraction is not allowed, because the meaning is never the same:

  • "Don't let's go to the movies!"

now is ungrammatical to the American, who believes that let's is sitting in a place where a subject-filled command should be.

(GEdgar's graph is explained by the rise of American)

  • 1
    I would give you an upvote for your first few paragraphs, but a downvote for '(Oh Providence!)'. It would be ungrammatical in your example, and in my view it's a simple subjunctive, or (for those people who don't believe English has a subjunctive) the first person equivalent of an imperative. Mar 2 '12 at 13:04
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    It is not ungrammatical. "Oh, providence, let us go to the movies." is perfectly normal English. The "let" is a command, and the only reason I put "Oh, providence" is to make it clear that mom is not the person who is doing the letting in this thing. It is absolutely not a subjunctive, because you would need a different verb there--- it's just a command with a neutral subject.
    – Ron Maimon
    Mar 3 '12 at 3:16
  • 2
    @TimLymington The mood you’re referring to is cohortative.
    – Jon Purdy
    Mar 16 '12 at 6:51
  • @Ron, sorry for probably repeating what you've wrote clearly, but you are really saying that most Americans will consider "Mom! Let's go to the movies!" as not a proposal for mom to go to the movies, but meaningless in this case "Mom!" and then a kind of talking-to-myself Oh God, let us go to the movies!? Aug 6 '12 at 22:54
  • @MaximV.Pavlov: not really, I am just saying that "Mom" is not doing any "letting" in the second part of the sentence. The "Mom" is clearly being let go to the movies, she is just not doing the letting. That's some abstract nonmentioned subject. Whether you are talking to yourself or not is not important, it could be either, but most likely you want Mom to go with you to the movies.
    – Ron Maimon
    Aug 10 '12 at 1:29

Your question brings to mind Alexandra Fuller's book "Don't Let's Go to the Dogs Tonight." I think the "don't let's.." construction is a plea: Please, oh please, let's not...

  • So the sentence construction would indicate a measure of exacerbation or urgency on behalf of the speaker?
    – BR79
    Mar 1 '12 at 22:44
  • Yes, it usually seems to.
    – JLG
    Mar 2 '12 at 17:34

The long form would be do not let us fight, which is perfectly acceptable and conveys the idea that the speaker would like to avoid an argument. Your question immediately put this song in my head.

  • "Do not let us fight" sounds so cumbersome compared to "Let us not fight," or "let's not fight." I guess maybe that was what made me think that it might not be proper usage. I've just never heard it used that way before. Thanks :)
    – BR79
    Mar 1 '12 at 22:29
  • I want to see others comment / agree with this answer, because this really is a tough case imo.
    – Frantisek
    Mar 1 '12 at 22:37

There is, as usual, a succinct summary in ‘The Cambridge Guide to English Usage’:

In its negative form this idiom becomes either Let us not (go into that), Let’s not (go into that) or, Don’t let’s (go into that). Once again they represent varying degrees of formality. The first has a slightly rhetorical flavour, which might be suitable for a formal document. The second is broadly useful for writing and conversation. The third is definitely chatty. Webster’s English Usage (1989) notes also let’s don’t as an American variant, though it goes with spoken rather than written discourse.

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