なくてはならない means must or have to. It is a JLPT N5 obligation pattern that sounds firm and a little formal: 「約束は守らなくてはならない。」 (Promises must be kept.)
Literally it says “if you don’t do it, it won’t do.” The first half (なくては) is “not doing,” and the second half (ならない) is “that’s not acceptable.” Two negatives make a strong positive: you have to do it.
なくてはならない — “not doing it is not an option.” The ならない ending gives it the weight of a rule.
What does なくてはならない mean?
なくてはならない expresses necessity or duty. Natural English versions are:
- must ~ — for rules and principles
- have to ~ — for practical necessity
- ~ is required / ~ is essential
It tends to describe obligations that come from outside the speaker: laws, rules, schedules, social expectations, or how things simply are. That is why you find it in rule books, instructions, and serious explanations more than in chatty conversation.
How to form なくてはならない
Start from the verb’s ない-form, drop the final い, and add くてはならない. In polite speech, change ならない to なりません.
- 守る → 守らない → 守らなくてはならない (must keep)
- 起きる → 起きない → 起きなくてはならない (must get up)
- 行く → 行かない → 行かなくてはならない (must go)
- する → しない → しなくてはならない (must do)
- 来る → 来ない → 来なくてはならない (must come)
The same ending also works after adjectives and nouns when you mean “must be”: 静かでなくてはならない (must be quiet), 学生でなくてはならない (must be a student). At N5 you will mostly see it with verbs.
When is なくてはならない used?
- Rules and laws: 「日本では、車は左側を走らなくてはならない。」
- Instructions: doctors, schools, and offices use the polite form: 「この薬は一日三回飲まなくてはなりません。」
- Personal duties described seriously: 「明日は朝六時に起きなくてはなりません。」
- Principles and morals: 「約束は守らなくてはならない。」
Register: the plain form ならない is typical of writing and formal statements. In polite speech, なくてはなりません sounds careful and correct. Between friends, people rarely say the full form. They shorten it to なくちゃ or switch to ないといけない, which feel much lighter.
なくてはならない example sentences
約束は守らなくてはならない。
Promises must be kept.
日本では、車は左側を走らなくてはならない。
In Japan, cars have to drive on the left.
この薬は一日三回飲まなくてはなりません。
You have to take this medicine three times a day.
明日は試験なので、今晩勉強しなくてはなりません。
I have a test tomorrow, so I have to study tonight.
図書館の中では、静かにしなくてはならない。
You must be quiet inside the library.
水は生活になくてはならないものです。
Water is essential to life.
Example 6 is a special use worth knowing. Here the なく comes from ない in the sense of “there isn’t,” the opposite of ある, so なくてはならないもの literally means “a thing you can’t be without” — something indispensable. You will meet this phrase in reading passages about health, nature, and technology.
Nuance of なくてはならない
Compared with the other “must” patterns, なくてはならない feels objective and weighty. The speaker is not just saying “I need to”; they are presenting the obligation as a rule, a fact, or a moral duty. That makes it great for signs, manuals, and statements of principle, and a bit stiff for everyday chat.
Tone depends on who is speaking. From a teacher or a notice, 「レポートは金曜日までに出さなくてはなりません。」 sounds like an official requirement. Said about yourself, 「帰らなくてはなりません。」 is a polite, slightly formal way to excuse yourself: “I’m afraid I have to go home.”
Don’t drop the く: the pattern is ない → な + くては. Watch the difference between なくてはならない (must do) and てはならない (must not do). One small く changes the meaning completely.
なくてはならない vs なくてはいけない
なくてはいけない is formed the same way and also means “must.” Most of the time you can swap them, but they lean in different directions.
Think of ならない as “it’s the rule” and いけない as “it’s not OK in this case.” If you are writing an essay or reading a sign, expect ならない. If a friend tells you why they can’t come out tonight, expect いけない, ないといけない, or なくちゃ.
Common mistakes with なくてはならない
Drop the い of ない before adding くては: 飲まな + くては.
“Must not” is て-form + はならない. なくてはならない means you are required to do it.
To say “no, you don’t have to,” switch to なくてもいい. Repeating the obligation says the opposite.
Not wrong grammatically, but it sounds like a written rule. Casual speech uses the short form なくちゃ.
Is なくてはならない on the JLPT?
Yes. なくてはならない is taught with the N5 obligation patterns, and it also appears at N4 next to なければならない. On the test it shows up in reading notices (“You must bring…”) and in grammar questions that check the ない-form conjugation.
At N5 you should be able to:
- Build the form from any verb’s ない-form
- Tell “must do” (なくてはならない) from “must not do” (てはならない / てはいけない)
- Answer “do I have to?” questions with なくてもいい
On reading tasks with notices or rules, sentences ending in なくてはなりません list what you are required to do. They often point straight to the correct answer.
Practice questions for なくてはならない
Show answer
学生は制服を着なくてはならない。 — Students must wear a uniform.
Show answer
明日、銀行に行かなくてはなりません。 — I have to go to the bank tomorrow.
Show answer
待たなくてはならない。 — (I) must wait.
Show answer
いいえ、来なくてもいいです。 — No, you don’t have to come.
Learning path for なくてはならない
Related grammar to review next
- なくてはいけない — the everyday twin; learn when いけない sounds more natural than ならない.
- なくちゃ — the casual contraction you’ll actually hear from friends.
- なくてもいい — “you don’t have to,” the natural reply to a “must I?” question.
- てはいけない — “must not”; keeps you from confusing prohibition with obligation.
- なければならない — the N4 version with the same meaning and register.
Learn なくてはならない with Hane
Hane drills なくてはならない next to なくてもいい and てはいけない, so “must,” “don’t have to,” and “must not” stay clearly separate. Practise with Hane.
FAQ about なくてはならない
What does なくてはならない (nakute wa naranai) mean in Japanese?
なくてはならない (nakute wa naranai) means “must do; have to do”. It is JLPT N5 grammar. なくてはならない expresses necessity or duty.
How do you form なくてはならない (nakute wa naranai)?
Start from the verb’s ない-form, drop the final い, and add くてはならない. In polite speech, change ならない to なりません.
What is the difference between なくてはならない and なくてはいけない?
なくてはならない: objective, formal. なくてはいけない: situational, conversational.
What is an example sentence with なくてはならない (nakute wa naranai)?
約束は守らなくてはならない。 — Promises must be kept.