Friday, November 1, 2019

jodoushi 助動詞

In Japanese, jodoushi 助動詞 are the morphemes suffixed to the six basic forms of verbs and adjectives in order to conjugate them into more complex forms.

For example, in nomaserarenakatta 飲ませられなかった, "[I] didn't let [you] make [me] drink [it]," there are four jodoushi: the past ta, the negative nai, the passive rareru, and the causative saseru, thus, the verb nomu 飲む, "to drink," is in its past, negative, passive, causative form.

In English, jodoushi is often confusingly translated as "auxiliary verb." There are various types of auxiliary verbs in Japanese, and jodoushi are the ones that least look like verbs. I mean, nai is an adjective, and even the ~ta ~た of past forms is a jodoushi.

In dictionaries, it's abbreviated to jodou 助動.


For reference, a list of jodoushi 助動詞 and their respective functions. Note: taberu 食べる, "to eat," is an ichidan verb, while nomu 飲む, "to drink," is a godan verb.

  • ~ta ~た, after ren'youkei.
    Past form.
    • tabeta
      Did eat. Ate.
    • nonda
      Did drink. Drank.
    • kawaikatta
      Was cute.
  • ~te ~て, after ren'youkei.
    Connective form. Conjunctive form.
    • tabete
      To eat, and...
      Eat [it]. (sometimes used as an imperative.)
    • nonde
      To drink, and...
      Drink [it].
    • kawaikute
      To be cute, and...
  • ~nai ~ない, after mizenkei.
    Negative form.
    • tabenai
      To not eat.
    • nomanai
      To not eat.
  • ~(sa)seru させる, after mizenkei.
    Causative form.
    • tabesaseru
      To make eat. To let eat.
    • nomaseru
      To make drink. To let drink.
  • ~(ra)reru られる, after mizenkei.
    Passive form.
    Potential form.
    • taberareru
      To be eaten.
      Can eat.
    • nomareru
      To be drunk. (doesn't mean to drink too much alcohol, like it means in English.)
      Can drink.
  • ~tai ~たい, after ren'youkei.
    Desiderative form.
    • tabetai
      Want to eat.
    • nomitai
      Want to drink.
  • ~masu ~ます, after ren'youkei.
    Polite form.
    By the way, the ren'youkei is sometimes called the "masu stem" because it's literally the stem of this jodoushi.
    • tabemasu
      [I] will eat [it].
    • nomimasu
      [I] will drink [it].
  • ~u ~う, after mizenkei.
    Volitional form.
    Sometimes hypothetically.
    • tabeyou
      Let's eat.
    • nomou
      Let's drink.
    • yokarou
      Very well. Alright.
    • nani ga arou to
      No matter what happens.
  • ~nu ~ぬ, after mizenkei.
    Negative form. Same meaning as ~nai ~ない, but its usage is different.
    • nomanu
      [I] won't drink [it].
  • ~n ~ん, after mizenkei.
    A contraction of ~nu ~ぬ.
    • shiran
      [I] don't know.
    • keshikaran
      Not appropriate.
      Scandalous. Outrageous.
  • ~yagaru ~やがる, after ren'youkei.
    To have the nerve to do something.
    • uso wo tsukiyagaru
      To have the nerve to tell a lie.
  • da だ, after nouns and the root of na-adjectives.
    • kore da
      This is [it].
    • kirei da
      [It] is pretty.
  • desu です, after nouns and the root of na-adjectives.
    This is the polite variant of da だ.
  • ~sou da ~そうだ, after ren'youkei of verbs, stem of adjectives.
    Seems like.
    • shini-sou da
      [It] looks like [he's going] to die.
    • benri-sou da
      [It] seems useful.
    • oishi-sou da
      [It] seems delicious.
  • ~you da ~ようだ, after rentaikei. Works basically like a noun.
    To seem like.
    • jikan ga kakaru you da
      It seems like [it] will take time..
  • ~rashii ~らしい, after shuushikei of verbs, stem of adjectives.
    I heard that. It seems that.
    • koko ni kuru-rashii
      I heard that [he] will come here.
    • oishii-rashii
      I heard that [it] is delicious.
    • kirei-rashii
      I heard that [it] is pretty.


The grammar of jodoushi is extremely weird, for several reasons.

To begin with, in Japanese, verbs, adjectives, and even the jodoushi themselves, have six different basic forms they can be conjugated to. Actually, it's more than six, but there's only six names for them. They are:

  1. mizenkei
    Irrealis form.
    • noma 飲ま
    • nomo 飲も
  2. ren'youkei
    Conjunctive form.
  3. shuushikei
    Predicative form.
    • nomu 飲む
  4. rentaikei
    Attributive form.
    • nomu 飲む
  5. kateikei, or izenkei
    仮定形, 已然形
    Hypothetical form. Realis form.
    • nome 飲め
  6. meireikei
    Imperative form.
    • nome 飲め

As you can see above, it's a mess. Some terms apply to multiple forms. Some forms apply to multiple terms, and which term it is, exactly, depends on how the word is used. For example, if a verb is used predicatively, it's shuushikei, but if it's used attributively, it's rentaikei.

Furthermore, ichidan verbs and godan verbs have different forms. See: ichidan vs. godan.

The important thing about these six forms is that they don't have a jodoushi in them.

For example, the past form of taberu 食べる, "to eat," is tabeta 食べた, "ate." In this past form, which you'd imagine is the simplest form possible, there's already a jodoushi in it: the ta た. Similarly, the negative form has a jodoushi, too.

In fact, you can't even use some forms without a jodoushi. For example, the mizenkei form doesn't mean anything on its own. Only when you add something to it, it can be used in a phrase.

  • *juusu wo noma
    (this is grammatically wrong.)
  • juusu wo nomanai
    To not drink juice.

The meireikei, "imperative form," on the other hand, can be used without jodoushi:

  • juuzu wo nome!
    Drink juice!
  • yasai wo tabero!
    Eat the vegetables!

So these jodoushi are an essential, but distinct part of the Japanese conjugation system.


The jodoushi are suffixes. Like all suffixes, they can be affected by changes in pronunciation, like rendaku 連濁 and sokuonbin 促音便. Unlike most suffixes, however, the jodoushi are affected by changes in pronunciation even weirder than normal.

Fortunately, this only applies to the jodoushi ~ta ~た and ~te ~て suffixed to godan verbs. Unfortunately, those are basically everywhere.

Both attach to the ren'youkei form of godan verbs, which ends with ~i.

  • korosu
    To kill.
  • koroshi-ta

  • koroshi-te

    Kill [him]. Kill [me]. Kill [someone].

The above is the ONLY godan verb that works as you'd expect. All other godan verbs work unexpectedly.

The godan verbs with ~ru ~る, ~tsu ~つ, and ~u ~う endings become tta った and tte って instead. This is called sokuonbin.

  • kau. katta. katte.
    買う. 買った. 買って
    To buy. Bought. Buy [it].
  • katsu. katta. katte
    勝つ. 勝った. 勝って
    To win. Won. Win [it].
  • karu. katta. katte
    狩る. 狩った. 狩って
    To hunt. Hunted. Hunt [it].

The godan verbs with ~ku ~く endings become ~ita ~いた. The ones with ~gu ~ぐ endings become ~ida ~いだ. This is called i-onbin イ音便. The ~ta ~たbecoming ~da ~だ is called renjoudaku 連声濁.

  • kaku. kaita.
    書く. 書いた
    To write. Wrote.
  • oyogu. oyoida.
    泳ぐ. 泳いだ
    To swim. Swam.

Except for iku 行く, "to go," which becomes itta 行った, "went," instead.

The godan verbs with ~mu ~む, ~bu ~ぶ, and ~nu ~ぬ endings become ~nda んだ. This is called hatsuonbin 撥音便.

  • nomu. nonda.
    飲む. 飲んだ
    To drink. Drank.
  • asobu. asonda.
    遊ぶ. 遊んだ
    To play. Played.
  • shinu. shinda.
    死ぬ. 死んだ
    To die. died.
Past form conjugation of godan verbs. 殺す, 殺した, 書く, 書いた, 泳ぐ, 泳いだ, 遊ぶ, 遊んだ, 死ぬ, 死んだ, 読む, 読んだ, 切る, 切った, 買う, 買った, 勝つ, 勝った, 行く, 行った. The くぐ endings are affected by イ音便. くぐぬむ are affected by 連声濁. ぶぬむ are affected by 撥音便. るうつ, and the verb 行く are affected by 促音便.

There is, unfortunately, a reason why it all ended up like this.

If you say nomi-ta, asobi-ta, shini-ta very quickly, they kind of merge together, and you end up with nonda, asonda, and shinda, respectively.

The same thing happens with kaki-ta, oyogi-ta, kari-ta, kachi-ta, kai-ta, and so on. The sound before ta た either partially merges with it, or gets skipped, and turned into a double consonant, into a sokuon 促音, represented by the small tsu.


The jodoushi have an important role in agglutination in Japanese.

You conjugate a word to a basic form, and then attach a jodoushi to it. You'd think it ends there, however, you can also conjugate the jodoushi.

  • kodomo ni yasai wo tabesaseru
    To make a child eat vegetables.
  • kodomo ni yasai wo tabasasero!
    Make the child eat vegetables! (this is an order!)

Above, the causative jodoushi saseru has been conjugated to its imperative form, sasero.

Since you attach jodoushi to basic forms, and you can also conjugate jodoushi to basic forms, that means you can also attach jodoushi to other jodoushi.

  • taberareru
    To be eaten.
    • Here, rareru is attached to the mizenkei of taberu.
    • This is the passive form.
  • haha ni yasai wo tabesaserareru
    To be made eat vegetables by [one's] mother.
    • Here, rareru is attached to the mizenkei of saseru.
    • And saseru is attached to the mizenkei of taberu.
    • This is the passive causative form.
  • yasai wo tabesaserarenakatta
    To not have been made eat vegetables.
    • Here, ta is attached ren'youkei of nai.
    • And nai is attached to the mizenkei of tabesaserareru.
    • This is the past negative passive causative form.

This looks a bit complicated, but once you get the hang of it, it's actually very easy.

That's because everything that ends with ~ta ~た is in the past form. It's not like English, where the past of drink is drank, and the past of eat is ate, of freeze, froze, see, saw, cry, cried, swim, swam, and so on. It's always, ALWAYS, ~ta ~た, except when it's ~da ~だ.

  • nonda
  • tabeta
  • kootta
  • mita

  • naita
  • oyoida

Similarly, if a complex form is in the past form, it will end in ~ta ~た, too.

  • taberareta
    Was eaten.
    • Past passive.
  • tabenakatta
    Did not eat.
    • Past negative.

Likewise, everything that ends with ~nai ~ない is in negative form. Everything that ends in ~nakatta ~なかった, consequently, is in past negative form. And so on.

Some jodoushi, like ~saseru and ~rareru, are conjugated like ichidan verbs. Others, like ~nai and ~tai, are inflected like i-adjectives. But that's not all.

Some jodoushi have weird conjugations, where they have some of the six forms, not all, and only for some very complicated grammar reason. For example:

  • tabetara
    If [you] ate.
    • This is the conditional ~tara ~たら form.

This tara-form is composed of the ~ta ~た jodoushi, which creates the past form, conjugated to its kateikei form, which is ~tara ~たら.

Similarly, ~zu ~ず, which translates to "without," is the ren'youkei of the ~nu ~ぬ jodoushi:

  • tabezu
    Without eating.
  • nomazu
    Without drinking.

The kateikei of ~nu ~ぬ is ~ne ~ね, and can be found in phrases like this:

  • yaranai
    To not do.
  • yaranu
    (same meaning as above.)
  • {yaranakereba naranai} koto ga aru
    [I] have something [that] {not doing can't be}.
    [I] have something [that] {[I] must do}.
    • nakere - kateikei of nai.
  • {yaraneba naranai} koto ga aru
    (same meaning as above.)
    • ne - kateikei of nu.

The same thing happens with masu:

  • tabemasu
    To eat.
    • masu - the polite jodoushi.
  • tabemasen
    To not eat.
    • masen - not a jodoushi.
    • mase - the mizenkei of masu.
    • n - the contraction of the negative nujodoushi.
  • tabemashita
    Did eat.
    • mashita - not a jodoushi.
    • mashi - the ren'youkei of masu.
    • ta - the past jodoushi.


The copulas da だ and desu です are classified as jodoushi in the dictionaries.

Under this analysis, the conjugation of da だ would look like this:[だ - 精選版 日本国語大辞典, via, accessed 2019-11-01.]

  1. mizenkei
    daro だろ
    dara だら
  2. ren'youkei
    da' だっ
  3. shuushikei
  4. rentaikei
  5. kateikei
    nara なら
  6. (it doesn't have a meireikei.)

Another analysis could be that da だ is the predicative copula, na な is the attributive copula, ni に is the adverbial copula, and de で is the te-form of the da だ copula.

Note that this conjugation includes some words that look completely different from da だ. This happens because, for example, ni に doesn't come from da だ, but functionally it works like the ren'youkei form of da だ, so we call it the ren'youkei, because it works like the ren'youkei.

But why are there three different ren'youkei for this thing?

That's because ta た attaches to the ren'youkei to form the past form. Since the past form of da だ is datta だった, that means da' だっ must be a ren'youkei, otherwise ta た wouldn't attach to it.

  • kirei da
    Is pretty.
  • kirei datta
    Was pretty.

Similarly, the ren'youkei of i-adjectives, which ends in ~ku ~く, works like an adverbial form. For na-adjectives, and nouns, the equivalent would be ni に. Therefore, ni に must be the ren'youkei form of da だ, too.

  • kawaiku naru
    To become cute.
  • kirei ni naru
    To become pretty.

Furthermore, the ren'youkei form of i-adjectives can attach to "support verbs," hojo-doushi 補助動詞, like aru ある, "to exist," and, in particular, its irregular negative form, nai ない, "nonexistent." Since the same thing happens to de で, it must be the ren'youkei, too.

  • {kawaikunai} neko
    A cat [that] {is not cute}.
  • kawaiku wa aru ga...
    Cute, [it] is, but...
  • {kirei de nai} neko
    A cat [that] {is not pretty}.
  • kirei de wa aru ga...
    Pretty, [it] is, but...

Note that the copula, unlike basically everything else, has a shuushikei that is different from its rentaikei. Observe:

  • neko ga shaberu
    The cat talks.
  • neko ga kirei da
    The cat is pretty.
  • {shaberu} neko
    The cat [that] {talks}
    The talking cat.
  • {kirei na} neko
    The cat [that] {is pretty}.
    The pretty cat.

As you can see above, if a word comes before a noun, the attributive form, rentaikei, is used, but if it's the predicate for a subject, the predicative form, shuushikei, is used instead. For verbs and i-adjectives, that form is the same, but for the copula it's different.

Note that, if you say {shabetta} neko 喋っ猫, "the cat [that] {talked}," then you have the rentaikei form of the jodoushi ta た, which, as you can see, is identical to its shuushikei: neko ga shabetta 猫が喋っ, "the cat talked."

Other Auxiliaries

Not everything that comes after a verb or adjective is a jodoushi.

For example, although the nai ない in the negative form of verbs is a jodoushi, the nai ない in the negative form of i-adjectives is not. It's a hojo-doushi, or hojo-keiyoushi 補助形容詞, "support adjective," instead.

One difference between these two things is that you can't put the wa は particle between a jodoushi and its stem, but you can do it with support words.

  • nomanai
    [I] won't drink it.
  • *noma wa nai
  • tookunai
    [It] is not far.
  • tooku wa nai
    Far, [it] is not.

So, despite looking like the same thing, they are different things.

Other words that are not jodoushi:

  • nomi-nasai
    Drink [it].
  • nomi-yasui
    Easy to drink.
  • {mizu wo nomu} toki
    When {[you] drink water}.
  • nomu-n-da
    Drink [it].
    • n-da - a a contraction of no da, which is the no の nominalizer plus the da だ copula.
  • nomeba
    If drinks [it].
    • ba - a conjunctive particle. This is called the ba-form.
  • nomeru
    Can drink.

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