Obligations and prohibitions: How to say “have to” and “must not” in Japanese?

The negative conditional is the “if you don’t [...]” form. It will always end in 〜なければ[nakareba], which gives us the first part of our obligation phrases.

To create the negative conditional, start with the plain negative form, and replace the final 〜ない[nai] with 〜なければ[nakereba]. This works for verbs, adjectives, and nouns.

ならない[naranai] and いけない[ikenai] are words that we use to indicate that something is not allowed. The two have the same overall meaning, but they carry slightly different implications:

• ならない[naranai] sounds more formal and objective. You’ll more often use this one if the need or obligation is due to rules or social norms.

• いけない[ikenai] sounds more conversational and subjective. You’ll more often use this one if you the speaker personally feel that it’s a need.

When you want to talk about a past need or obligation (e.g. “I had to”) or when speaking politely, you’ll change the form of these verbs.

There are three main situations where you can use 〜なければならない[nakereba naranai] or 〜なければいけない[nakereba ikenai].

• To describe the speaker’s own obligation: “I have to…”

  We can use either 〜なければならない[nakereba naranai] or 〜なければいけない[nakereba ikenai] to describe our own obligation:

  歯が痛いので、歯医者に行かなければならない / いけない.

  Ha ga itai node, haisha ni ikanakereba naranai / ikenai.

  I have to go to the dentist because my tooth hurts.

  If you’re talking about your own past obligation, (e.g. “I had to”), 〜なければならなかった[nakereba naranakatta] will sound a little more natural than 〜なければいけなかった[nakereba ikenakatta]:

  今朝は５時に起きなければならなかった。

  Kesa wa go ji ni okinakereba naranakatta.

  I had to get up at 5 o’clock this morning.

  We can use either structure when asking or answering a question.

  Speaker A:

  本を借りるには会員でなければなりません / いけませんか。

  Hon o kariru ni wa, kai’in de nakereba narimasen / ikemasen ka.

  Do I have to be a member to borrow books?

  Speaker B:

  はい、会員でなければなりません / いけません。

  Hai, kai’in de nakereba narimasen / ikemasen.

  Yes, you have to be a member.

  If the answer to the question is “no,” though, you’ll need to use another expression, such as 〜なくてもいい[nakute mo ii](not have to) as below:

  Speaker B:

  いいえ、会員でなくてもいいです。

  Iie, kai’in de nakute mo ii desu.

  No, you don’t have to be a member.

• To remind a listener of their obligation: “You have to…”

  When reminding the listener of their obligation, there is a slight difference between the two obligation phrases:

  • 〜なければいけない[nakereba ikenai] sounds stronger and more coercive, more like a command.

    野菜も食べなければいけませんよ。

    Yasai mo tabenakereba ikemasen yo.

    You also have to eat vegetables, OK?

  • 〜なければならない[nakereba naranai] sounds softer, more like a reminder.

    レポートは金曜日までに出さなければなりませんよ。

    Repōto wa kin’yōbi made ni dasanakereba narimasen yo.

    You have to submit the paper by Friday, OK?

  Important

  Though 〜なければいけない[nakereba ikenai] is softer than 〜なければいけない[nakereba naranai], it’s still mostly used when you have authority over the person you’re talking to: it sounds strong. It’s best to avoid using either expression when addressing a “superior” such as a teacher, boss, or customer.

  Sometimes you might also use these expressions to remind your listener about someone else’s obligations. For example:

  Mother:

  さつきとめい、今日またけんかしたのよ。

  Satsuki to Mei, kyō mata kenka shita no yo.

  Satsuki and Mei had a fight again today, you know.

  Father:

  うーん、二人とも、もっと仲良くしなければいけないね。

  Ūn, futari tomo, motto nakayoku shinakereba ikenai ne.

  Hmm, those two have got to get along with each other better.

  → Here, 〜なければいけない[nakereba ikenai] sounds more natural because the speaker is expressing a strong opinion.

• To state rules or general obligations: “People must…”

  To state rules and general obligations, we can use either 〜なければならない[nakereba naranai] or 〜なければいけない[nakereba ikenai].

  • A rule:

    図書館では静かにしなければなりません / いけません。

    Toshokan de wa shizukani shinakereba narimasen / ikemasen.

    You must be quiet in the library.

  • A general obligation:

    人には親切でなければなりません / いけません。

    Hito ni wa shinsetsu de nakereba narimasen / ikemasen.

    We must be kind to other people.

  When talking about “natural laws” or things that always “just happen,” usually 〜なければならない[nakereba naranai] will sound more natural.

  • ✅ 生き物はいつか死ななければならない。

    Ikimono wa itsuka shinanakereba naranai.

    Living creatures must die some day.

    → This isn’t a rule, really, it’s just describing how things are.

  • ❓ 生き物はいつか死ななければいけない。

    Ikimono wa itsuka shinanakereba ikenai.

There are several other ways you can express obligation in Japanese, most of which are variants of the two we’ve discussed above. Let’s go through the most common ones. 〜なくては[...nakute wa] / 〜ないと[...nai to]

• 〜なくては [nakute wa] and 〜ないと [nai to]

  When speaking more conversationally, you can replace the negative conditional ending 〜なければ[nakereba], with 〜なくては[nakute wa] or 〜ないと[-nai to].

  • もう帰らなくてはいけません / なりません。

    Mō, kaeranakute wa ikemasen / narimasen.

    I have to go home now.

  • 寝る前に歯をみがかないといけないよ。

    Neru mae ni ha o migakanai to ikenai yo.

    You have to brush your teeth before you go to bed.

  NOTE:

  〜ないと[-nai to] will usually be paired with いけない[ikenai], not ならない[naranai]!

  In everyday conversation, you can actually use 〜なくては[nakute wa] or 〜ないと[nai to] without including the final verb, and that doesn’t change the meaning.

  • すみません。もう帰らなくては。

    Sumimasen. Mō kaeranakute wa.

    I’m sorry. I have to go home now.

  • ほら、寝る前に歯をみがかないと。

    Hora, neru mae ni ha o migakanai to.

    Hey, you have to brush your teeth before you go to bed.

• 〜なきゃ [nakya] and 〜なくちゃ [nakucha]

  In casual conversation, you can use the following contractions of 〜なければ[nakareba] or 〜なくては[nakute wa].

  Full form	Contraction
  〜なければ nakareba	〜なきゃ nakya
  〜なくては nakute wa	〜なくちゃ nakucha

  Like the full forms, the contractions can be used before the verbs ならない[naranai] or いけない[ikenai]:

  • 一緒にジョギングしたいなら、朝６時に起きなきゃならないよ。

    Isshō ni jogingu shitai nara, asa roku ji ni oki nakya naranai yo.

    You’ve got to get up at 6:00 in the morning if you want to go for a jog with me.

  • もう着るものがないから、洗濯しなくちゃいけない。

    Mō kiru mono ga nai kara, sentaku shinakucha ikenai.

    I’ve got to do my laundry since there are no clean clothes left.

  But in more casual conversation, these verbs can actually be omitted.

  • あ、もう帰らなきゃ。

    A, mō kaeranakya.

    Oh, I’ve gotta go home now.

  • 遅刻するよ。ほら、急がなくちゃ。

    Chikoku suru yo. Hora, isoganakucha.

    You’ll be late. You’ve gotta hurry now.

  NOTE:

  When the final verb is omitted, 〜なくちゃ[nakucha] sounds rather feminine and is most often used by female speakers.

• 〜ねばならない [neba naranai]

  〜ねばならない[neba naranai] is an old-fashioned expression that is often used to discuss obligations in formal speech or writing.

  国民は国を守らねばならない。

  Kokumi wa kuni o mamoraneba naranai.

  Citizens must protect their nation.

  But though it’s usually formal, some people will also use 〜ねば[neba] on its own, in more casual contexts, in a jokey way:

  夏休みもあと少しだね。宿題やらねば・・・😱😱😱

  Natsuyasumi mo ato sukoshi da ne. Shukudai yaraneba… 😱😱😱

  The summer break will be over soon, won’t it? I must work on my homework… 😱😱😱

  Important

  Please note that when using the irregular verb する[suru](to do) along with ねば[neba], we need to use not the “regular” nai-form し[shi] (which connects to ない[nai]), but the alternative (classic) nai-form せ[se] as in せねば[seneba].

  もうすぐテニスの試合。もっと練習せねば・・・😅

  Mōsugu tenisu no shiai. Motto renshū seneba…

  The tennis tournament is fast approaching. I must practice more…

We can use 〜てはいけない[-te wa ikenai] or its polite form 〜てはいけません[-te wa ikemasen] in the following situations:

• General rules or moral prohibitions: “People must not….”

  te-formforbidding verb

  A rule:

  学校では廊下を走っては いけません。

  Gakkō de wa rōka o hashitte wa ikemasen.

  We must not run in the hallways at school.

  A moral prohibition:

  人の悪口を言っては いけません。

  Hito no waruguchi o itte wa ikemasen.

  We must not speak ill of other people.

  Tip

  If you’re talking about a rule that existed in the past, it will sound more natural to replace いけない[ikenai] with なりません[naranai]. We’ll give some examples below!

• To tell someone not to do something: “You are not allowed to...”

  te-formforbidding verb

  ジョンさん、授業中に漫画を読んではいけませんよ。

  Jon san, jugyōchū ni manga o yonde wa ikemasen yo.

  You must not read comic books during the class, John.

  With context, you can sometimes drop the forbidden action + は[wa], and just use the いけない[ikemasen] part, though it sounds a bit curt:

  Child:

  ママ、おやつ食べてもいい？

  Mama, oyatsu tabete mo ii?

  May I eat some snacks, Mom?

  Mother:

  今は、いけません。

  Ima wa, ikemasen.

  Not now.

  lit. As for now, you must not.

  Important

  〜てはいけない[te wa ikenai](must not) is a strong statement. It should only be used by authoritative figures (e.g., parents, teachers, doctors, bosses) toward people in their charge (e.g., children, students, patients, subordinates). For example, a teacher may tell their students:

  宿題にチャットボットを使ってはいけません。

  Shukudai ni chattobotto o tsukatte wa ikemasen.

  You must not use a chatbot for your homework.

  To soften the tone, we may use 〜てはいけないことになっている[...te wa ikenai koto ni natte iru](is/am/are not supposed to…) instead. This is a round-about way of expressing a prohibition toward the listener, indicating that it’s a general rule–a decision made not by the speaker but by someone else:

  宿題にチャットボットを使ってはいけないことになっています。

  Shukudai ni chattobotto o tsukatte wa ikenai koto ni natte imasu.

  You are not supposed to use a chatbot for your homework.

There are some related expressions for prohibition.

• 〜てはならない [te wa naranai]

  When forbidding an action, you can replace the forbidding verb いけない[ikenai] with ならない[naranai], but it sounds more formal and is more often used in writing or formal speech.

  te-formforbidding verb

  ここで写真を撮っては なりません。

  Koko de shashin o totte wa narimasen.

  You must not take photos here.

  You’ll often see ならなかった[naranakatta] used when discussing past rules or moral prohibitions. In this case, it will sound more natural than using いけなかった[ikenakatta].

  te-formforbidding verb

  昔、女の人は富士山に登っては ならなかったそうだ。

  Mukashi, on’na no hito wa Fujisan ni nobotte wa naranakattasō da.

  I’ve heard that women were not allowed to climb Mt. Fuji in the old days.

• 〜てはだめだ [...te wa dame da]

  If you’re directly telling someone not to do something, you can use だめだ[dame da] in place of the forbidding verb. だめだ[dame da] is a casual phrase that means “not good” or “not allowed,” so you’ll generally do this in less formal contexts.

  te-formforbidding phrase

  めい、お父さんの仕事のじゃまをしてはだめだよ。

  Mei, otōsan no shigoto no jama o shite wa dame da yo.

  Mei, you must not interrupt your father’s work, OK?

  Remember, though, that you won’t use だめだ[dame da] if you’re establishing a general rule!

  The final だ[da] can be omitted, which softens the tone in casual conversation.

  te-formforbidding phrase

  お父さんの仕事のじゃまをしてはだめよ。

  Otōsan no shigoto no jama o shite wa dame yo.

  You must not interrupt your father’s work, OK?

  → This sounds feminine.

  Please note that when the sentence-ending particle such as よ[yo] is added directly after だめ[dame], it sounds rather feminine and is mostly used by female speakers.

• 〜ちゃ [cha] or 〜じゃ [ja]

  When making prohibitions, you can also use a for 〜ては[te wa] or 〜では[de wa] in conversation.

  Full Form	Contraction
  〜ては te wa	〜ちゃ cha
  〜ては te wa	〜じゃ ja

  When making prohibitions, you’ll only use these contractions alongside いけない[ikenai] or だめだ[dame da].

  contractionforbidding expression

  甘いものばかり食べちゃいけないよ。

  Amai mono bakari tabecha ikenai yo.

  You must not eat so many sweets (and nothing else).

  この川で泳い じゃだめだよ。

  Kono kawa de oyoija dame da yo.

  You must not swim in this river.

  However, we can switch the word order as below in casual conversations to get to the point (“YOU MUST NOT!”) right away. The English translation stays the same.

  forbiddingcontraction

  だめだよ、この川で泳いじゃ！

  Dameda yo, kono kawa de oyoija!

  You must not swim in this river!