When you’re learning a language, you often talk about all the things you will do as you express your likes or agree to help others. And learning to talk about things you won’t do is just as important! If you ever want to convey the word “not” in Japanese, you’ll need nai-form.
Japanese conjugations are typically made by adding different suffixes to the dictionary form of a verb or adjective, and that includes making an affirmative word (like “will read”) into a negative one (like “won’t read). That’s where the nai-form Japanese conjugation comes in: It’s used for making verbs and adjectives negative by adding the suffix –nai (～ない).
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Japanese nai-form is the plain negative conjugation of verbs and adjectives
Japanese has conjugations for different levels of politeness and formality, and nai-form (nai-kei, ない形) is the plain (or casual) negative conjugation for verbs and adjectives. At the end of a sentence, nai-form is usually casual rather than polite (which would use masu-form, the standard Japanese verb conjugation).
However, nai-form has other uses that can be used at any level of formality and in any situation. For example, here’s what nai-form and masu-form would look like for the verb iku (行く), or “to go”:
- dictionary form: iku (行く)
- nai-form: ikanai (行かない)
- masu-form: ikimasen (行きません)
The verb tenses Japanese uses are divided into past tense and non-past tense, which includes talking about the present and the future. Nai-form is simply the conjugation for making a word negative, and it’s in the non-past tense by default, but it can be further conjugated into other tenses and forms from there, including past tense.
How to conjugate Japanese words to negative form using nai
Japanese has a few different types of nai-form conjugations, which each have their own rules:
- ichidan (一段), godan (五段), and irregular Japanese verbs
- desu (です), which is “to be” in Japanese
- Japanese adjectives (i-adjectives and na-adjectives)
The good news is that all of them end in –nai, so you only need to learn how to connect it to the dictionary form to conjugate them correctly.
Japanese nai-form conjugation for ichidan verbs
Conjugating ichidan verbs to nai-form is simple. Just drop the –ru (～る) at the end of the dictionary form of the verb and add –nai in its place.
- taberu（食べる）→ tabenai（食べない）
- to eat → don’t/won’t eat
Japanese nai-form conjugation for godan verbs
To conjugate godan verbs into nai-form, look at the last character of the dictionary form of the verb. You’ll need to change the final sound from an “u” sound to an “a” sound in the same hiragana row and then add –nai. For example, you’ll change gu (ぐ) to ga (が) and tsu (つ) to ta (た) before adding –nai.
Verbs that end in u (う) are the exception. For these verbs, change the u to wa (わ) instead of a (あ).
- kau（買う）→ kawanai（買わない）
- to buy → don’t/won’t buy
- kaku（書く）→ kakanai（書かない）
- to write → don’t/won’t write
- oyogu（泳ぐ）→ oyoganai（泳がない）
- to swim → don’t/won’t swim
- hanasu（話す）→ hanasanai（話さない）
- to speak → don’t/won’t speak
- matsu（待つ）→ matanai（待たない）
- to wait → don’t/won’t wait
- yobu（呼ぶ）→ yobanai（呼ばない）
- to call → don’t/won’t call
- yomu（読む）→ yomanai（読まない）
- to read → don’t/won’t read
- hashiru（走る）→ hashiranai（走らない）
- to run → don’t/won’t run
Irregular Japanese nai-form conjugations
You need to know three unique nai-form conjugations. The first two are for the two Japanese irregular verbs for “to do” and “to come.” The third is the nai-form for aru (ある), which means “to exist.” Even though it’s typically conjugated like a godan verb, its nai-form is unique.
| Dictionary Form | Nai Form | English |
| する suru | しない shinai | to do/don’t or won’t do |
| 来るkuru | 来ない konai | to come/don’t or won’t come |
| ある aru | ない nai | to exist/don’t or won’t exist |
Japanese nai-form conjugation for ‘to be’
The two ways to conjugate desu into nai-form are de wa nai (ではない) and ja nai (じゃない). The meaning is identical, but ja nai is the contracted form of de wa nai. This makes de wa nai a little more formal and academic, while ja nai is casual. Think of this as being the same difference as using “is not” or “isn’t” in English.
De wa nai is primarily used in written language when it isn’t being used in a casual conversation.
- Boku wa hitsuji ni sawaru no ga kowai desu. Demo sensei wa kiken de wa nai to iimasu.（ぼくは羊にさわるのが怖いです。でも先生は危険ではないと言います。）= I am afraid to touch the sheep, but my teacher says it is not dangerous.
Meanwhile, ja nai has a conversational tone and is used in spoken and written language alike. It’s likely that you’ll come across ja nai more often than de wa nai.
- Boku wa hitsuji ni sawaru no ga kowai desu. Demo sensei wa kiken ja nai to iimasu.（ぼくは羊にさわるのが怖いです。でも先生は危険じゃないと言います。）= I am afraid to touch the sheep, but my teacher says it isn’t dangerous.
Japanese nai-form conjugation for adjectives
Adjectives require conjugating just like verbs in Japanese. How you conjugate Japanese adjectives to nai-form depends on whether you’re using an i-adjective or a na-adjective.
To conjugate i-adjectives to nai-form, drop the –i (～い) at the end of the word and add –kunai (～くない).
- atsui（暑い）→ atsukunai（暑くない）
- hot → not hot
Conjugations for na-adjectives are really just adding the appropriate conjugation for desu after the adjective. For nai-form, that means putting de wa nai or ja nai directly after the adjective without adding na.
- shizuka desu（静かです）→ shizuka de wa nai（静かではない） or shizuka ja nai (静かじゃない)
- quiet → not quiet
Conjugate nai like an i-adjective for other forms
Like masu-form, nai-form starts as the non-past tense by default, but you can also conjugate it into other common forms like past tense and te-form. Conveniently, they conjugate the same way as i-adjectives: drop the –i at the end and add the appropriate conjugation.
The Japanese past tense conjugation for nai-form requires you to swap the –i for –katta (～かった).
- nomanai（飲まない）→ nomanakatta（飲まなかった）
- drink → drank
For the Japanese te-form, swap the –i for –kute (～くて).
- nomanai（飲まない）→ nomanakute（飲まなくて）
- drink → drink [and]
How to create nai-form Japanese sentences
You can use conjugated verbs and adjectives in nai-form in the same way you would use any other plain form conjugation. For example, you can use it to:
- end a sentence in negative form
- describe nouns as “not” something
- ask a question or seek agreement
- request that someone not do something or go without something
End a sentence in nai-form
The most straightforward use of nai-form is to use it with the main verb of a sentence, making it negative. Following typical Japanese word order, this would put nai-form at the very end.
For verbs, you have three main options for sentences in negative form:
- Casual: nai-form
- Somewhat polite: nai-form + desu
- Polite: masu-form
Once you know what level of politeness you need for your situation, you conjugate the sentence accordingly.
- Gakkō ni ikanai.（学校に行かない。）= I’m not going to school. (casual)
- Gakkō ni ikanai desu.（学校に行かないです。）= I’m not going to school. (somewhat polite)
- Gakkō ni ikimasen.（学校に行きません。）= I’m not going to school. (polite)
You can also do this with adjectives at the end of a sentence. You can make the sentence polite by adding desu to the end, or you can leave it as just the adjective in nai-form to make it casual. Modern Japanese doesn’t have a masu-form for adjectives.
- Kanojo wa tsuyokunai desu.（彼女は強くないです。）= She’s not strong. (polite)
- Kanojo wa tsuyokunai.（彼女は強くない。）= She’s not strong. (casual)
Describe nouns with nai-form
In Japanese, you can describe nouns with adjectives in two primary ways. First, you can make the noun the subject and put the adjective at the end. Alternatively, you can put the adjective before the noun.
The adjective can be positive (left as dictionary form) or negative (conjugated to nai-form) while staying in front of the noun. This is unlike how English uses negative adjectives, where it often uses an antonym for the adjective or changes the order of the noun and adjective.
- atarashii hon（新しい本）→ atarashikunai hon（新しくない本）
- new book → book that is not new (literally: not-new book)
To use it in a sentence, you can insert the new adjective-noun pair wherever the noun fits in your sentence.
- Muzukashikunai shukudai ga suki desu.（難しくない宿題が好きです。）= I like homework that is not difficult. (Literally: I like not-difficult homework.)
Asking questions in nai-form
In casual conversation, you can end a sentence in nai-form with a rising intonation to ask a question or seek agreement. It’s similar to adding “isn’t it?” to the end of a question in English.
- Ano eiga, sugokunai?（あの映画、すごくない？）= That movie is awesome, isn’t it?
This form is also frequently paired with particle no (の) at the end of a sentence, which asks for an answer or explanation.
- Shiai wa ashita ja nai no?（試合は明日じゃないの？）= The match isn’t tomorrow?
Use nai de to make requests or say ‘without’
The te-form of –nai is –nakute, but another similar form is –nai de. It sounds similar to te-form, so it’s easy to get the two mixed up. The –nai de suffix has two primary uses: giving instructions not to do something and saying “without.”
Giving warnings and directions not to do something are usually done by using the –nai de form (as shown below) or by using the word kinshi (禁止), which is specifically used on signs prohibiting certain actions.
- Hashiranai de. Gakkō no naka de wa, arukanakereba ikemasen.（走らないで。学校の中では、歩かなければいけません。）= Do not run. You have to walk inside the school.
You can also add kudasai (ください), which is one of the ways to say “please” in Japanese, to make the request more polite.
- Hashiranai de kudasai.（走らないでください。）= Please do not run.
To use –nai de to say “without,” note that the verb with –nai de will not be the main verb of the sentence. Instead, –nai de will go earlier in the sentence like a separate dependent clause.
- Benkyō shinaide tesuto ni gōkaku shita no?（勉強しないでテストに合格したの？）= You passed the test without studying?
What does the word ‘nai’ mean in Japanese by itself?
On its own, nai means “doesn’t exist” as it is the nai-form of the verb aru (to exist). In English, this often translates to similar words related to “no” in Japanese, like “not,” “none,” or “nothing.”
- Sumimasen. Kono chikaku ni ATM wa arimasu ka.（すみません。この近くにATMはありますか。）= Excuse me. Is there an ATM near here?
- Nai to omoimasu yo.（ないと思いますよ。）= I’m sorry. I do not believe that there is. (Literally: I think there is not.)
Key takeaways about the Japanese nai-form
On the surface, the nai-form Japanese conjugation is simple. It’s a negative conjugation in the same way English would insert “not” before a verb or adjective. The important thing is to remember how to create those conjugations.
- The nai-form in Japanese is also called the plain negative form.
- Drop the final –ru and add –nai for ichidan verbs, and change the final “u” sound to an “a” sound and add –nai for godan verbs.
- Drop the final –i and –kunai for i-adjectives and add the nai-form of desu (de wa nai or ja nai) to na-adjectives.
- The nai-form can be further conjugated into other forms by dropping the –i at the end and adding other suffixes.
- You can also use nai-form to ask questions casually or request that someone not do something.
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