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"il ne faut pas ..." or "ne pas devoir" ?

i dont know if somebody's already asked this so i'm sorry if this is a repeat ! i couldnt find a previous post

anyways. i am a little confused about the two phrases "il ne faut pas" and "ne pas devoir"

which one means "must not" and which one means "not have to" ? do they each have different meanings ?

like if i say "il ne faut pas que tu y ailles" - does that mean A) "you must not go (you absolutely cannot go)" or does it mean B) "you do not have to go (but you could, you just don't particularly have to)"

if i say "tu ne dois pas y aller" - would that one mean A or B ? or do the french not differentiate between these two small differences and use both interchangeably just like their positive forms ?

(i never know if i make sense or not when i explain myself so if this makes no sense please tell me) thank you :) <3

March 16, 2018



Both mean "You must not go".
To express "You don't have to go" it would be "Tu n'as pas à y aller".
To express "You don't need to go" it would be "Tu n'as pas besoin d'y aller".

There is more information on expressing obligation here:


I agree in a non specific way that they both mean "You must not go".

However there is also a nuance in definition.

  1. You must not go - due to external forces there is not a need, and it is important that the end result of leaving should not occur.
  2. You must not go - due to external forces, there is no obligation, yet the focus is on the action, that it is the act of leaving that should not occur.
  3. You must not go - due to internal forces, there is no need. That it is perceived by someone else that there is no need within yourself that should require you to leave.

Thus in reverso you get a translation for :
Tu n'as pas besoin d'y aller. : as "Nobody expects you to, really."

Which I interpret as being more in line with nuance 3.

However I am still learning French, so if there are other definitions and factors I should be considering, please correct me.


Unfortunately, we have no further context to apply nuances to.

PS Thanks for the heads-up ☺


good point.

Yet it is good ( and for me fun ... yes I am bizarre at times ;P ) to try to understand these nuances. I enjoy being aware of them. And I do also support discussions of detail about such nuances.

It often amazes me the detail of accuracy of different concepts that are often used in French. That it opens up new ways to look at an issue.

It gives me interesting new concepts to ponder and new ways to see the world.

Thank you for putting up with my desire to understand the meaning behind the words, and the value of selecting the correct word for the meaning you may want to express.


From what I understand :

  • falloir : is for necessities, needs. It focuses the action. So if it is more important that the task is completed, it would be more appropriate to use this word.
  • devoir : is for obligations, duties. It focuses on the person who needs to do the action. If it is more important that the individual does something, then, this would be be better word to use. It is indicating that this person must do it for an external reason, and the focus is on this person doing it.

However the result is often the same. Which is why it is often seen as interchangeable.

Another verb to express need that is frequently used is:
avoir besoin de : to need
And it is indicating that there is a need from within that person to do something.

A further layer to this for falloir is :

For falloir it is only used in the third person singular impersonal expression : Il faut.

  • As such it is often used to talk about a general rule or a general statement that is applied to people, and not to an individual.

  • It can be used for a specific person, if you include an indirect object pronoun.
    me, te, lui, nous, vous, leur

However your question is all about the negative.

I hope I have got this all correct , and look forward to input from others.

If I find more discussions in Duolingo about this - I will return and add them here.


To me, "Il ne faut pas" means "You mustn't" in the sense of "One mustn't", e.g. Il ne faut pas vendre la peau de l'ours avant de l'avoir tué (Don't sell the bear skin before you've killed the bear = Don't count your chickens...).

"Tu ne dois pas" usually means "You (personally) mustn't, but can also mean "You (personally) don't have to". If it's not clear from the context you mean "You don't have to", you say "Tu n'est pas obligé de...". e.g. "Tu n'est pas obligé d'y aller si tu ne veux pas".

The impersonal form "On est pas obligé de" is also common.


Thank you peterviuz !

You are a STAR !

I am here to learn language.
I am not a qualified expert in any language.
I am a native speaker of English. Though I have not qualified in scholarly terms with the technical aspects of English, though I hold a degree, and am a driven (mad) poet. (p.s. just ask even most people here ;P )

Thank you for sharing this.


You are very kind. I am not a language expert either, I just have the enormous advantage of having lived in France for many years!

I realise I have used the common spoken form "On est pas obligé de", whereas the more correct form is "On n'est pas obligé de".


Duolingo is an open community here. And frequently it is observed that often the most helpful and engaging patient and informative explanations are provided by learners.

Duolingo also has marvelous academics here, that we treasure enormously, as well as teachers. Also due to the fact we are an open community.

I feel a bit self conscious wearing my ring of responsibility, and am continuing to address the issue of getting the balance right between the authority that does need to represent, and to not misrepresent that authority to imply what it is not in my case.

My role with the ring is a moderator on this platform, though it is not across all forums. I also assist in a technical and group dynamic way with one of the language teams, which I am honored and fascinated to be able to serve.

There is a passion I also have to be able to make learning available to others without cost. And as such am inspired by the manefesto of Duolingo. And in that, I have created also a string of resources that I have ound useful for my French learning and given it the "tag" of Learning Loom I actively promote others to also create interesting posts about aspects of grammar in languages. And also to arrange them in a useful way that over time they can hopefully be found by people, when they wish to learn more about a particular grammar aspect of the language they are learning.


Bonjour, je voulais juste vous remercier, "peterviuz", pour une réponse apportée A une question posée ...Comme je n ai pas su rejoindre la discussion concernée, je le fais ici en espérant que vous puissiez en prendre note. Merci pour votre bienveillance.


Mais de rien! En fait vous pouvez voir toutes les discussions auxquelles vous avez participé, dans "Discussions". Pour moi, le site s'affiche en anglais, donc je ne suis pas sûr comment ça s'affiche en français. En anglais, on choisit "Followed", donc peut-être "Suivi" (à droite).



anyways. i am a little confused about the two phrases "il ne faut pas" and "ne pas devoir"

From my reading and understanding, to the most part they can be used interchangeably, especially if you are referring to yourself.

However you will find scattered through the internet, and also within Duolingo, that the phrase "il ne faut pas" is a highly used one. I think that is is also because it is not as direct, and thus is also perhaps more polite.

So when referring to someone else - it is better to use "il ne faut pas". And also for being able to not be as direct, it can be useful to use when referring to yourself.

While if you use "ne pas devoir" it is not as polite for someone to say to someone else. Though it could be relevant for a person to say about themselves. That for external reasons they feel they must do something, or not do something if you use "ne ... pas".

As is also "avoir besoin de" , to express a need within themselves to do, or to not do something if you use "ne ... pas".

As always, if I have got the wrong end of the stick, I hope someone will correct me.



like if i say "il ne faut pas que tu y ailles" - does that mean A) "you must not go (you absolutely cannot go)" or does it mean B) "you do not have to go (but you could, you just don't particularly have to)"

I think it is A)
And that the reason is because of external issues.
And there are examples of this from reverso

if i say "tu ne dois pas y aller" - would that one mean A or B ? or do the french not differentiate between these two small differences and use both interchangeably just like their positive forms ?

I think it is more like you must not go, because it is something that you must not do.
That it is due to an obligation to the external world that you need to observe.

And here are some examples from reverso.༠

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