"Have to", "must" and "should"
なければならない is "must" and "have to": word for word, "if I don't, it won't do". It is the one to learn first, and most of the other forms say the same thing: shorter ones for conversation, an older one for formal writing. べきだ is different: "should", a judgment of what is right and not a rule.
| Form | What it says | Where |
|---|---|---|
| なければならない, なくてはならない | "Must", "have to" | Rules, notices, writing, careful polite speech |
| なければいけない, なくてはいけない | The same | Everyday speech, plain or polite |
| なくちゃ, なきゃ | The same, cut short: "I've got to" | Friends, family, talking to yourself |
| ないと | "If I don't…", with the rest left unsaid | Conversation and messages; ないと |
| べきだ, べきではない | "Should", "should not": what you believe is right | Newspapers, debates, essays; everyday talk too |
| こと, ending a line | A rule, as it is written down | School rules, notices, exam papers |
| ねばならない | "Must", in an old form | Editorials, essays, speeches, novels |
なければならない, なくてはいけない: the full forms
Full pageなければならない・
なければ and なくては are both "if not", and ならない and いけない are both "it won't do". All four combinations mean the same; ならない leans to rules and writing, いけない to everyday speech. The polite ending is なりません, and "had to" is ならなかった.
a rule
In the library, you must turn off your cell phone.
your own situation
I have an early start tomorrow, so I have to go to bed now.
Said directly to someone, all four tell them what to do, and to your boss that can sound like an order.
なくちゃ, なきゃ, ないと: in conversation
Full pageなければならない・
なくちゃ is short for なくては, and なきゃ for なければ; they mean the same. ないと is "if I don't…". All three often end the sentence, because everyone knows the rest. Said like that, they are mostly about yourself: something you just remembered, or why you are leaving. English often says "I've got to" or "I should".
We're out of milk. I have to buy some on the way home.
I should study more.
The train is about to leave. I have to go.
To ask a question, to say "had to", or to tell someone else what to do, the rest comes back: いけない, or the casual だめ.
a question
Do I have to finish the homework today?
a polite question
Do I have to come tomorrow too?
had to
Yesterday I had to work until nine.
to someone else, in polite speech
You need to write your name on this document.
I have to get up early tomorrow.
With いけないんです after it, なきゃ is heard in polite conversation too.
なきゃ, ないと or なければなりません?
It is time to go home. What you say depends on who you are with.
Sorry, I have to be going soon…
Trailing off: a soft way to leave, in polite company too.
I have to be going.
To a teacher or a host. To a friend it sounds like reading out a rule.
Where it goes wrong
With two negatives in it, なければならない looks like "must not". It is "must", and 行かないと is "I have to go", not "I'm not going". "Don't have to" and "must not" have endings of their own.
You have to take your shoes off here.
Not taking them off won't do.
You don't have to take your shoes off here.
Not taking them off is fine.
You must not take your shoes off here.
Taking them off won't do.
べきだ: should, as a judgment
Full pageべきだ・
べきだ says what the person speaking believes is right. That is stronger than advice.
Experts should honestly admit what they don't know.
Said to someone about how they should behave, it can sound like a sermon, even when you mean a friendly tip, and it is not something to say to a teacher or a boss. と思います makes it your opinion.
One of my staff keeps making the same mistake.
I think you should hear what they have to say first.
I should have seen a doctor sooner.
べきだった is "should have": regret, or blame.
"Should not" is べきではない. The verb stays positive.
Not said: そんな
(You shouldn't say things like that.)
言うべきではない.
Three phrases you'll hear
やるべきことthings to get done
I have a lot to get done today.
べきかどうかwhether I should
I can't decide whether I should quit my job.
絶対…べきyou really must
You have to see this movie.
Between friends, a warm recommendation and not a sermon.
たほうがいい, べきだ or なければならない?
Telling someone to apologize, at three strengths.
You'd better apologize soon.
Advice. Things will go better for you.
You should apologize soon.
A judgment. It is the right thing to do.
You have to apologize soon.
No choice. A rule or the situation demands it.
たほうがいい is the everyday "you should": the other person can still choose.
こと: the last word of a written rule
Full pageことだ・
A line that stops at こと, with no だ or です, is a written rule. In conversation the same rule is てください or てはいけません.
Always turn off the power after use.
Do not run in the hallways.
With だ after it, ことだ is advice, not a rule: "the thing to do is…".
ねばならない: must, in an old and solemn form
Full pageねばならないN2
ねばならない means what なければならない means: ねば is an old way to say なければ. する becomes せねばならない.
This record must be preserved for the future.
The usual form in writing and careful speech.
This record must be preserved for the future.
The same duty, said solemnly: a speech, an essay, a vow.
Other kinds of "must" and "should"
必要があるN4Matter-of-fact
"Need to", stated as a fact, as offices and doctors put it. For your own errands, people say ないと.
For safety, the power needs to be turned off before starting work.
しかないN3
"Have no choice but to": every other option is gone.
The last train has already left, so we have no choice but to take a taxi home.
に違いないN3Confident
"Must" as a sure guess, never "have to".
The lights are off and there is no answer. They must have gone to bed already.
はずだN4What you expect
"Should" meaning "I expect so".
According to the schedule, the train should arrive at ten.