At an elementary level, often, Japanese learners are taught that です is equivalent to the verb "to be" in English. Typical example:

私は学生です, I am a student.

That's fine, after all, it works. And to be honest, most people probably wouldn't really need a different explanation for the rest of their life.

With this question I'd like to go a little deeper. Can we really call です(or だ) an auxiliary verb?

To start with, if you look だ up on goo, it is grouped together with です, である, and のだ.

Right off the bat, you get this explanation:

断定を表わす。 expresses a conclusion/decision

So here is not really mentioning the word "verb" or "auxiliary verb" at all. Shortly after you can see:


So, we can start by saying that actually です is an alteration/contraction of でございます.

Continuing to read the definition we get:


Hence, 「である」 is formed by attaching to「で」the subsidiary/auxiliary verb「ある」. Because actually:

「で」は「だ」の連用形。 「で」is the conjunctive/continuative form of 「だ」

Therefore, if I'm not wrong, we can do the following passages:

「で」+「あります」=「であります」= 「でございます」 = 「です」

Does the above make sense? In particular I'm a bit doubtful about the second equality.

To sum it up, 「です」 is a variation of 「だ」(its polite form). It is also a contraction of 「でございます」, which in turn is the same as 「であります」(forgetting here about the differences in usage), that is formed by attaching 「で」 to the verb「あります」.

So, after this long trip, we arrive to the conclusion that the "hidden verb" behind 「です」, is in fact ある, which is actually (or at least more close to) the sought after "to be".

Is this a correct explanation? How can it be improved? Or, if it's wrong, where and why?

3 Answers 3


Your collection of questions conflate a few things: 1) what is だ・です in modern Japanese, and 2) how did だ・です derive historically.

Because of #2, #1 is a bit ... messy. :) So let's start with the history.


This isn't an explanation of what です is now, so much as an explanation of the historical derivation. Shogakukan's 国語大辞典 provides this description:


Meanwhile, the modern plain form だ derives as:


Modern で (which actually appears from around the 1300s-1500s) is understood to have evolved from earlier にて (which is still used in formal writing). Classical copular ("is") verb あり equates to modern verb ある.

Looking now at the particular parts of your post:

「で」は「だ」の連用形。 「で」is the conjunctive/continuative form of 「だ」

Well, yes, in the modern language. But historically, だ derives from で + ある -- so this is not a regular kind of conjugation paradigm.

To sum it up, 「です」 is a variation of 「だ」(its polite form).

Yes. Though I might not use the term "variation" so much as "polite form".

It is also a contraction of 「でございます」,

It derives from a contraction of でございます, but I don't believe it's considered to be such a contraction in modern regular usage.

which in turn is the same as 「であります」(forgetting here about the differences in usage)

It's not quite the same as であります. Note that ございます is the humble version of あります. That difference in usage is important. :)

that is formed by attaching 「で」 to the verb「あります」.

Yes -- but note also that であります is not a verb unto itself, but simply the particle で plus the verb あります.

So, after this long trip, we arrive to the conclusion that the "hidden verb" behind 「です」, is in fact ある, which is actually (or at least more close to) the sought after "to be".

Historically, yes. And if you dig around in classical Japanese and older stages of the language, you'll find just that -- あり serves as the primary copular verb.

In modern Japanese, however, だ・です is the primary copular verb: it closes a predicate, and (optionally) supplies social register information ("politeness"). One no longer says things like 綺麗にあり, one says instead 綺麗だ. Similarly, instead of 本にてあり, one says 本だ.

Related thread touching upon social register:

I hope the above covers the bases for you. If not, please comment and I can edit the post accordingly.


I missed a question of yours that I'd meant to answer.

Can we really call です(or だ) an auxiliary verb?

Depends. :) "Auxiliary verb" (助動詞) is a kind of loose category in Japanese school grammars. The article on the Japanese Wiktionary provides a table showing the various things that get this label. Some of them I really don't agree with: そうだ and ようだ are listed here, and those are clearly そう or よう + copular だ・です -- and だ・です is right there in the table as it's own pair of rows at the bottom. Others like らしい, ない, and たい are adjectival in form and function. Many, like させる or たがる, have full conjugation paradigms (i.e. they have forms for all conjugation slots), whereas others like negative supposition まい or positive supposition う are defective (i.e. have incomplete conjugation paradigms; see Defective verb at Wikipedia).

Basically, it's a grab-bag of odds and ends that get stuck on the ends of other things (often, but not always, verbs). This category was also previously called simply 助け言葉 ("helping words"), and this vague moniker is a clue to the vagueness of the category itself.

So, "can we really call です(or だ) an auxiliary verb?" Sure. So long as we're clear on what we mean by "auxiliary verb". :)

  • 2
    Actually I think this is a great answer. Very helpful to clarify what my understanding was. I think I wasn't really far away from the right answer, and was looking just for some remarks like yours to put everything in the right place. It's quite a shame stuff like this is not covered in most of Japanese language books. Sometimes I have a feelings things are "simplified" just to get the reader to get the point.. but they should talk about this stuff somewhere.
    – Tommy
    Commented Nov 5, 2018 at 7:23
  • 1
    As a side note, I don’t believe it’s known for sure whether です is actually from でございます, or whether it’s from であります, でおわす, でする, etc. All of them exist(ed) side by side, and all of them tend(ed) to be paired down to shorter versions; which of them, if any one in particular, ended up being standardised as です is a highly complex question that may not have an answer at all. Commented Nov 5, 2018 at 11:26
  • 1
    @JanusBahsJacquet, agreed -- I thought I'd read somewhere about であります as the basis for です, but when I went looking, I found only the でございます shift above, and a shift from でそうろう → でそう → です. Shogakukan's entry states that the latter was limited to 狂言, which seemed irrelevant here so I didn't add it to my post. From what little I've read about Japanese in the Edo period and earlier, でございます seemed to be used more in speaking than であります, making it more likely that speakers would abbreviate that construction. OTOH, language is nothing if not complex; です could be from "all of the above". ¯_(ツ)_/¯ Commented Nov 5, 2018 at 16:48
  • 2
    @Tommy, ya, it would be nice if more of this stuff were available (easily findably, anyway) in English. That said, any textbook explanation has to draw the line somewhere, or run the risk of drowning its readers in excessive detail and turning them off altogether. I'm personally fascinated by etymologies and historical shifts over time, and I'm spending (probably far too much) time over at Wiktionary, mostly adding etymologies to entries by translating the info I can find in Japanese-only sources -- precisely because I was stymied by the lack of same in materials for learners. Cheers! Commented Nov 5, 2018 at 16:54
  • 2
    Erik and @Tommy – if you’re interested in easily accessible Japanese etymology and don’t already know about it/own it, I can recommend Bjarne Frellesvig’s A History of the Japanese Language (Cambridge UP). Very useful and well-written book with a plethora of interesting details! Commented Nov 5, 2018 at 17:03

To address some points raised:


Honorific language is a hodge-podge of verb forms and locutions used to show respect. The fact that the polite past tense of the copula でした is used to create the polite past tense of 読みません is just an accident of historical usage. Originally there were other competing forms: -ませなんだ, -ませんかった, -ませんだった, in addition to -ませんでした. The polite past tense form of the copula is being used only to convey politeness, with no regard to its formal meaning as a copula. One might compare the use of the causative form of the verb to indicate extreme politeness that is common in classical Japanese. To try and force some causative sense from it would be fruitless. And then there is the causative-passive in classical Japanese...

Generally, the longer a locution, the more it is percieved as being polite. This tendency is found in English (at least as spoken by British English speakers) as well, 'Can you close the door please?', 'Would you be so kind as to close the door please?', 'May I trouble you to close the door please?' etc. English can't rely on many special verb forms unlike Japanese.


だ・です can be split, だ => である です => であります, and then additional material can be inserted. One can say 昨日は学生ではあった・ありました, 'yesterday I was a student'. (There is some kind of implied comparison here, 'yesterday I was a student [but today...]', but the sentence can stand on its own, since context will make it clear.) One can also say 昨日は学生でもあった・ありました 'yesterday I was also a student'. Further examples:

だから中国は専制君主制の国家でながくありましたけれども・・・ 'Thus China was long a county under an absolute ruler, but...

吃音{どもり}で、無口な暴君でわたくしがあれば・・・ 'If I were to be some stammering, speechless tyrant...'


Since one can find many examples of acceptable Japanese such as




it would appear difficult to claim that 気を本当に付ける is not acceptable. There is a syntactical operation in Japanese known as 'scrambling' (かき混ぜ操作) whereby sentential constituents such as noun phrases, adverbial phrases, can be moved from one position in the sentence to another. 本当に is an adverbial phrase, and can be freely moved. Reasons for scrambling are probably to do with shifting emphasis around in the sentence. An example:

a. 喫茶店の主人が元町商店街で犯人らしき男を見たそうだ。

b. 元町商店街で,喫茶店の主人が犯人らしき男を見たそうだ。

c. 犯人らしき男を,喫茶店の主人が元町商店街で見たそうだ。

d. 元町商店街で,犯人らしき男を,喫茶店の主人が見たそうだ。

a. is the normal, unmarked order of constituents. b., c., and d., show a constituent moved to the front of the sentence, presumably to highlight that constituent.

The case of 気を本当に付ける is thus nothing more than an example of the above operation.


I'd like to address another item where there seems to be further, terrible confusion in regard to the use of です.

The following list of sentences, cited above, is suppose to show that treating だ・です as the copula is misleading:







本当に?私もですよ。[as answer to the above]


As discussed earlier, the polite forms of the copula are used as a suppletive device to form honorific forms of verbs which otherwise don't exist; thus, there is no polite past tense form of the verb, so でした is added to the negative of the non-past form, 読みませんでした to make a polite past tense. To think of it as the copula here is a mistake. Similarly, でしょう is added to a non-past (or past) tense verb to create a dubitative/tentative form, 読むでしょう, since 読もう, as pointed out, is hortative, 'let's [do]'.

The case of お読みですか is somewhat different. This is the same as お読みになりますか, and one can see that the copula is being substituted for the string になります. Here it is reasonable to treat です as the copula; if one were to force a translation, 'is it your esteemed reading?'

In 私はですね, we have an example of one of the many ways of stating a topic in Japanese. The sense overall is no different from 私は:

私はですね、この本を読みたいんです = 私はこの本を読みたいんです

A literal translation into English of course is unnatural, 'it is me [and]', but that is the basic sense in Japanese.

Further, sentence ending のです means 'it is a case of', 'the explanation for [something in context] is that', or the like. It is also often used when there is a hint of reserve or hesitation, so it is commonly used with ーたい like this, frequently also followed by が・けど:

その映画を見に行きたいんですが I would like to go and see that movie but [would you like to come too?]

私もですよ demonstrates how です, as a copula, can be used as a substitute for a constituent in the same, or a previous sentence:

私もですよ = 私も[読みたいんです]よ 'it is me too [who wants to read it]'

In あの子にじゃなくて、あなたにあげる we have the same usage. Without substitution it would be


English is similar: 'I will give it to you, and not [give it to] her'.

読まないとです makes no sense as it stands. The only way to make sense of this syntax is with some context like this:

お暇があると、それを買ってくれない? 全然急ぎではないんで、お暇があるとですね。

If you have time, could you buy it for me? It's not at all urgent, so, [it's] if you have time, OK?

And here, です is the copula.

The standard reference for anything to do with Japanese grammar is Samuel Martin, A Reference Grammar of Japanese.

  • "The fact that the polite past tense of the copula でした is used to create the polite past tense of 読みません is just an accident of historical usage." I'm not sure I agree. The problem here is that the irregular ません conjugation for the negative doesn't have an obvious way to inflect to attach another component (if it were regular, like 読みまさない, we could predict 読みまさなかった, and it wouldn't feel like a compromise the way the other proposals do). Commented Sep 28, 2023 at 9:25
  • The forms listed are attested for the Edo period up to Meiji. There is no dispute about that. One only of them survived, the 読みませんでした form, for some reason to do with circumstances at the time, hence, by 'an accident of historical usage'. How can you disagree with that? Further we are not talking about a simple past tense negative, we are talking about a past tense negative with polite/honorific stylization, and so the Japanese resorted to the methods they did. If you feel they were 'compromising' in some way, then the study of Japanese is bound to cause you much grief.
    – N. Hunt
    Commented Sep 28, 2023 at 21:36
  • "How can you disagree with that?" What I disagree with is that it's accidental. I think the existence of the competing forms is a consequence of the fact that 読みません is irregular in the first place, and that the -せん ending doesn't offer an obvious way to continue the conjugation from there, in the way that a-stem + -ない does. "If you feel they were 'compromising' in some way, then the study of Japanese is bound to cause you much grief" I mean compromise in the sense that none of the choices is clearly the most sensible, and one is only preferred with the benefit of hindsight. Commented Sep 28, 2023 at 23:38
  • In 私はですね, we have an example of one of the many ways of stating a topic in Japanese. 「ですね」はよくfillerとしてインタビューや会議で文節に入りますよね。「ボディアーマーにはですね、分厚いセラミック板がですね、これだけでも結構重いんですが、~」「かつてはひどい凝り性でですね、首・肩の凝りがすごかったんですが、重いヘルメットを着けていたおかげでですね、首の筋肉が鍛えられまして、そういった凝りがですね、すべて解消してしまったんですね」 (1) 「あるいは有識者会議をですね、軽んじるつもりは全くないというようなことをですね、そういうことを前提にしてですね、聞いていただきたいと思います」 (2) その「ですね」もfillerではと思うのですがどうでしょう
    – chocolate
    Commented Sep 29, 2023 at 1:03
  • お暇があると、それを買ってくれない? 全然急ぎではないんで、お暇があるとですね。 doesn't sound natural. It should use あったら・あれば instead, as in 暇があったら、それを買ってくれない?全然急ぎではないんで、暇があったらです。 読まないとです。 -- I sometimes hear things like this in casual speech: 宿題しないとです、早く寝ないとです meaning ~しないといけません. I don't think it's grammatically correct, though.
    – chocolate
    Commented Sep 29, 2023 at 1:17

The problem is that in modern Japanese “〜である” and it's many forms can do many things it's elementary parts of “〜で" and “ある” cannot explain, the two are also inseparable when used in this meaning which is very often the case when adverbial forms of nouns are combined with other verbs, for instance, while in: “ナイフで切る” we can separate them and in theory write “ナイフで昨日に切った” to say “Yesterday I cut with a knife.” we cannot use “学生で昨日にあった” to mean “Yesterday I was a student.” there are many other such inseparable constructs such as “気をつける”, we can't say “気を本当につける” to mean “really watch out”, only “本当に気をつける”. In fact, an interesting thing is that it's even “お気をつけください”, not “気をおつけください”, which really shows how inseparable they are.

But the issue goes deeper, than that, you say that it simply means “to be” and that most people would never need to think of it otherwise. I believe that teaching students it means “to be” will very quickly require them to unlearn a couple of things, such as that they might encounter sentences such as:

  • “読みたいです。”
  • “読むでしょう。”
  • “読みませんでした。”
  • “読まないとです。”
  • “ご主人様はそれをお読みですか。”
  • “私はですね、この本を読みたいんです。”
  • “本当に?私もですよ。” [as answer to the above]
  • “あの子にじゃなくて、あなたにあげる。”

None of these are hyper-rare, far-fetched examples and in all of them, seeing “〜です”, or the last case the plain “〜だ” as “to be” makes no sense. Furthermore, in most of these examples “〜で” alone without coupled with “〜ある” wouldn't ever be grammatical, so what is actually going on here and what is “〜である” or “〜だ” doing in modern Japanese?

The simple theory that seems to fully describe “〜だ”'s function with no exception.

What it is is simple: It's a clitic that is used to conjugate sentences that end on a part of speech that can't conjugate itself to provide that specific conjugation.

It's simply temping of it to think of it as “to be” because the two most common completely nonconjugable parts sentences can end on, nouns and na/no-adjectives typically, but not always, carry a semantics that would be translated with “to be” in Japanese. But many other parts of speech also can't conjugate in Japanese, or not fully. Even verbs can't fully conjugate on their own to form the polite past negative form, they lack this conjugation so “読みませんでした” has to step in and add “〜でした” to complete it. i-adjectives lack their own polite forms completely so “読みたいです” has to step in. Things such as “〜私も” don't conjugate at all, so “〜私もだよ” or “〜私もだった” have to step and in modern Japanese the volitional form of active verbs has lost it's original meaning of creating a supposition so “読むだろう” has to step in to provide that because “読もう” simply means “Let's read.” not “He'll surely read.”.

Even with many na-adjectives it doesn't make much sense to think of it as “to be” rather than simply a part of speech that conjugates the na-adjective. For instance with “私はあなたを好きだ。”. Yes, I know that many traditional grammarists would object to the use of “〜を” here but the reality is that Japanese people use it nowadays, and not infrequently at all. Some would analyse “私はあなたが好きだ。” as actually being “To me, you are loved.” to cling on to the idea that “〜だ” means “to be” here but with “〜を”, which is used, this is really not possible any more, “好き” simply functions as a verb here with a subject and an object that means “to love”, there is no “to be”, but it can't conjugate on it's own, so it needs “〜だ” to assist it and for instance become negative:

好き clearly used as a verb with an object using 〜じゃない to become negative. [熱ぞトラップ ch. 7]

Essentially, if functions much the same as the now uncommon “〜を好かない” here. It can't be justified to mean “to be”, it simply serves to make a na-adjective, functioning as a verb, which are by the way called “descriptive verbs” in Japanese, negative.

So no, I don't believe it can be called an “auxiliary verb” as much as an “auxiliary conjugation”.

  • 「読まないです。」の「と」は、どういう意味ですか?
    – chocolate
    Commented Sep 28, 2023 at 13:04
  • 「読まないと」の丁寧な活用だ。「読まないといけないです」と同じ意味だ。「読むしかないです」という意味に近い。
    – Zorf
    Commented Sep 28, 2023 at 17:45
  • I think that 読まないとです, 私はですね, 私もですよ and あの子にじゃなくて are not grammatically correct.
    – jarmanso7
    Commented Sep 28, 2023 at 21:43
  • @jarmanso But we say things like these in (casual) speech. The ですね in 私はですね、~~ is a filler and often used in interviews, eg 私はですね、献金をしていただく場合はですね、(安倍晋三) I believe 私もですよ。is grammatically fine.
    – chocolate
    Commented Sep 28, 2023 at 23:53
  • @jarmanso7 they occur all the time however, and not simply in casual speech but relatively formal writing. The idea that they are not correct might stem from misconstruing “〜だ” as something that can only follow a noun or na-adjective. Just after I made this post, I played some Diabolik Lovers, in which レイジ, a character that speaks in very formal Japanese replied to to an accusation with “私がですか?”, meaning something like “You say I did it?” this is quite common which is why I don't believe “です” simply means “to be”.
    – Zorf
    Commented Sep 29, 2023 at 3:26

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