なくてはいけないMust do, Have to do

Also used to express duty or necessity. Click here if you are curious about なくて conjugation

Structure

Verb［ない］+ なくては + いけない
Verb［ない］+ なくちゃ + いけない

Details

Part of Speech
Expression
Word Type
Auxiliary Verb
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Formal

About なくてはいけない

Much like てはいけない, なくてはいけない states that something 'must not' be done. However, this is where the similarities end. なくてはいけない is an example of a double negative in Japanese, and actually has the meaning '(A) must be done', or 'must do (A)'.

While this grammar point is usually translated as 'must do', the literal translation is 'must not, not do (A)'. This double 'not' is where many learners have difficulties. いけない simply means 'cannot go', and comes from the negative potential form of 行(い)く.

To use this structure, simply create the negative form of a verb, and then convert ない to なく (the conjunctive form of an い-Adjective), followed by て. After this, は is added, and then finally いけない.

いけない is considered to be the most common structure used with the 'must', and 'must not' grammar points, and is natural in both speech, and written Japanese. Alternatively, ならない may be used in formal speech, but is much better suited to writing. だめ is also acceptable, but much more casual than either いけない or ならない.

Caution

The ては in なくては is often converted to ちゃ, as this is easier to say. なくちゃ may then be followed by いけない, or いけない may be omitted, without changing the meaning.

土曜日(どようび)も会社(かいしゃ)に行(い)かなくちゃいけない。

I gotta go to the company on Saturdays too.
今日(きょう)はスーパーに行(い)かなくちゃ。

Today, I gotta go to the supermarket.

These casual structures are very similar to words like 'gotta' in English.

Antonyms

Examples

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テストの前(まえ)に、よく寝(ね)なくてはいけない。

Before a test, you must sleep well.

１２月(じゅうにがつ)になってから、暖房(だんぼう)をつけなくてはいけない。

Once December comes, you have to turn on the heating.

来週(らいしゅう)は試合(しあい)があるので、たくさん練習(れんしゅう)しなくてはいけない。

Because I have a game next week, I must train a lot.

今日(きょう)はいい天気(てんき)だから、外(そと)で遊(あそ)ばなくてはいけない。

Because the weather is nice today, I have to play outside.

まだやりたいことがあるけど、もう寝(ね)なくてはいけない。

There are still things that I want to do, but I have to sleep already.

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なくてはいけない – Grammar Discussion

Most Recent Replies (21 in total)

Jake
must do, have to do
Structure
- Verb[ないく・て]・は・いけない
View on Bunpro
xBl4ck
The note on this grammar point (and all the other “must do” ones really) says the following:

[いけない = neutral ・ならない = formal/written・だめ = casual/conversational]

But both Japanese Ammo and Tae Kim say that いけない and ならない are the same when it comes to formality, but ならない is more objective (e.g. rules) and いけない is more subjective.

Edit: NihonOnTheGo phrases it quite nicely
The difference between ならない and いけない is that ならない implies a sense of obligation—as in it’s just something that has to be done; like paying taxes, obeying the laws, etc.—It’s inevitable. いけない, however, has a nuance that infers the “inconvenient consequences” of not doing something.

Did i missunderstand this in some way? And if so, what source is the Bunpro note pulled from? (So I can read up on it)
mrnoone
Hey

I completely agree with those descriptions.

The note will be changed soon.

Sorry for the inconvienience
Flyed
So what exactly is the difference between this grammar point and なくちゃ・なきゃ in terms of usage?
mrnoone
@Flyed

Hey and sorry for the late answer

なくちゃ is a contracted form of なくては and なきゃ is a contraction of なければ, in other words, they are more casual forms.
So when you want to be more casual, or say it faster, you go with those.

It is similar to I’m and I am in English.
conan
My Italki teacher used the construction ないといけない. It seemed to mean the same thing, but I couldn’t find this grammar on Bunpro. Just wanted to mention it here, if it’ll be considered worthwhile to add on its own or at least have a notation about it on similar grammar
mrnoone
Hey

It has been on the to-do list

For the time being, I will add information about it in “must do” grammar points!

Cheers!
conan
Oh awesome! Thanks so much x3
mrnoone
The information about the existence of ないといけない・ならない has been added to the “must” grammar points!
We will try to add the ないといけない and ナイトならない as fast as possible.
mrnoone
By the way, we have added ないといけない!
petepolack
Why is なければいけない marked wrong for these questions? What is the difference between なければいけない and なくてはいけない?
Pushindawood
@petepolack Hey! We throw hints for なければいけない answers because we have a separate grammar point dedicated to なければいけない and we want you to get ample practice with both variations. You should be seeing a hint to use なくて rather than なければ when typing your answer to lead you in the right direction. Both grammar points are very similar, and the difference between the two really only boils down to state (なくては) and possibility (なければ). Cheers!
marlowe
I’m just wondering why a double-negative construction is used in this grammar - it’s something that always trips me up and I feel if I had a better grasp on the why then it might stick in my head better.
Daigo
It’s likely to be a matter of culture. Instead of saying “must” or “have to”, which are a blunt way to convey being forced to do something, in Japanese we use something like “if this is not, it cannot go”,or in English terms: “It is not acceptable if this is not done”.

So tactful
marlowe
Ah okay, yes that makes sense - it’s ironic that Zen Buddhism is known for its directness yet the language goes out of its way to avoid that
FredKore
What if the Zen Buddhism is a reaction to the culture?
Marcus
Just a short question if I may … what is meant by “long form て”? I know (in theory at least) what the て-form is, but what is “long form て”, and is there also a “short form て” too?
Marcus
Me again, sorry! It’s just that I notice that this “long form て” comes up on every review question, and I’ve still not figured out what “long form て” means!
Marcus
“Colloquial short form of ば”

Okay, I’m utterly lost now. Typing this here rather than taking a hammer to my computer! lol!
nekoyama
This “long form” and “short form” isn’t a grammar term; it refers to whether bunpro wants an unabbreviated way to say “must” or a shorter, more colloquial one (e.g. なくてはいけない vs なくちゃ).

て and ば refer to which pattern to say “must” is used (…なくては… vs. …なければ…, and …ないと… also exists).

いく refers to which word is used in the second part (いけない / ならない / だめ) if one exists.