I was reading the wikipedia page on "predicate," where it mentioned that in Japanese, the negative form of a verb is an adjective. I thought that this was too expansive a statement to be true, but what does the writer mean? Does the writer mean that only verbs in the ない form of the negative are adjectives? Is this still too broad in meaning to be true?

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    Flamebait warning: Aren't all Japanese adjectives verbs anyway? :) I actually think this is an interesting question, from a practical "How should I categorize it to learn it" standpoint, from a historical "where did this ぬ ず ない confusion come from" standpoint, and a linguistic "Do other languages also have word classes that conjugate into other word classes" standpoint. Unfortunately, I don't have the knowledge to give a full answer.
    – dainichi
    Commented Feb 21, 2012 at 14:21

4 Answers 4


Arguing about whether certain words "are" something or other is missing the point in this context, I think. We do not classify words based on some innate, a priori nature that we discern within them. We classify them based on behaviour. And there is no a priori set of standards for that classification either: we have to choose our own. It's completely arbitrary. But if we aim to be scientific, we will generally want to choose standards that are as simple as possible while explaining as much as possible (with as few inconsistencies and exceptions as possible).

So, take the polite nonpast negative ending -nai. It ends in -i, like an adjective. It takes endings like -katta and -kereba like an adjective. It can be used adnominally or conclusively, like an adjective ("shiranai hito" vs "ano hito wa shiranai"). Particles like "kedo" and "shi" attach to it like an adjective. (Both of these last two points apply to verbs too, of course.) On the other hand it can't be passivised like a verb.

In short, we can list many ways in which it acts like an adjective, and many ways in which it doesn't act like a verb. On that basis, we might decide that it is simpler to just call it an adjective than a verb-in-disguise. We would advance a theory in which we have a category called "adjective" that includes words like "akai", "hiroi", "kanashii" but also "ikanai" and "shiranai".

On the other hand, objections can be raised. In this thread, Ian has raised some. I find them unconvincing (for the reasons given in dainichi's comments), but we can find other differences. For example, the "-ide" ending does not seem to be available to "natural adjectives": we can say "ikanaide" but not "akaide" or even "akakunaide". So we have to adjust our theory to account for this. Maybe we say "There are two kinds of adjectives, one natural and one derived from verbs via the -nai ending; they behave very similarly but we observe these differences..." Or maybe we say "Verbs in the negative nonpast remain verbs; they exhibit some very adjectivelike behaviour but we can tell the difference because..." We have to decide which theory fits the facts best, ideally in the sense of "best" described above (simplest, most powerful, etc.)

Now, all of the above said, let's look at the -masen ending. It doesn't seem to behave much like an adjective at all, except in very trivial ways So even if we define our category of "adjective" such that it includes words with the -nai ending, we probably won't put words with the -masen ending in there too. We could -- it's arbitrary! -- but doing so wouldn't help us explain very much. It would just make our theory more complicated. So, we don't.

Thus, what I think the wiki editor whose description you read meant was "once the plain nonpast negative ending -nai is attached to a verb, the resulting word behaves so much like an adjective that it makes more sense to classify it as one (in the classification scheme I am implicitly adopting)." Not "any negative verb phrase is an adjective by definition," or anything extreme like that.


Dainichi's comment on your question is another example of the principle that we are free to set up our categories in any way we like. Adjectives and verbs are obviously different in many ways, but there is also a sense in which they are similar. Given the structure "Hana wa X", a verb like "saku" could fit in there, or an adjective like "akai". They fit into the same "slot" like that. This isn't true of English; we can say "the flower blooms" but not "the flower red"; we have to say "the flower is red" (and, incidentally, for this reason most linguists working on English will recognize a category that contains both "blooms" and "is red").

So in that high-level sense, Japanese adjectives and verbs form a unified superclass of words, one that can be distinguished easily from, say, nouns, or particles. That isn't any less true just because we can subdivide that superclass into "verbs" and "adjectives" based on morphology. There might be cases where using this superclass makes things easier for us (e.g. looking at high-level syntactic patterns), and there might be cases where it's easier to keep verbs and adjectives distinct (e.g. looking at word endings). Neither analysis is wrong; they're just different tools for different tasks.


Modern Japanese is very different from archaic Japanese (and some modern formal written Japanese, which is itself rather archaic) in regard to the topic at hand. Initially there were distinct conjugations of verbs and adjectives known as predicative and attributive. Predicative (also called conclusive) was used for the final verb in a sentence, and was finite. The attributive form was used nominally and for relative clauses (remember that technically "adjectives" in Japanese are relative clauses), and seems to be non-finite. Rather than the modern -い ending of adjectives, adjectives had the ending -し in predicative form and -き in attributive (for modern ない that would give なし and なき, respectively).

For an example of this, and an example that shows this is still in use in written Japanese, take the title 藍より青し. Here, 青し is the predicative form of the adjective, with the original -し suffix.

At one point Japanese underwent a radical morphology change, and actually lost the predicative form entirely, completely replacing it with the attributive (at least in form; the semantic distinction between finite and non-finite remained). At this point a large number of old verb suffixes disappeared. The old negative suffix, for example, mostly disappeared, replaced by -ない (at some point the attributive -き suffix of adjectives was reduced to -い, as well). Presumably the old suffixes required finite verb forms, and were lost when the morphologically finite forms disappeared, replaced by the morphologically non-finite forms that had the same meaning (i.e. -ない).

Now, I imagine when you heard that negative verbs were adjectives this was based on the fact that ない is the head of the verb phrase for negative verbs and it's an adjective. This is indeed a change that occurred at one point, and was not always the case, as I spent the majority of this post explaining. My hypothesis is that the old suffixes used with predicative verbs were themselves predicative (auxiliary) verbs, and the old attributive and modern suffixes are in fact adjectives or nouns (or derived from them).

  • Since I can't seem to figure out how to commend on anything but my answer... dainichi: "Aren't all Japanese adjectives verbs anyway?" Yes and no. Linguistically they are verbs, but they are a distinct word class in Japanese. You can prove that by the fact that adjectives can only be inflected in a small subset of the ways verbs can - obvious example: adjectives cannot take -ます (and many other things). Historically, they appear to have originally been nouns, with suffixes (-し, -き/-い, -く) added to make them act like verbs. Commented Mar 23, 2012 at 3:48
  • It's worth noting that some languages do not have a clear lexical separation between verb, adjective, and/or noun, and the meaning of a word depends on where it appears, rather than its lexical class. I'd wager Japanese initially had only nouns and verbs: nouns acted like adjectives through agglutination, and like verbs through zero-copula constructions; later, suffixes were added to the nouns to produce an adjective word class with explicit morphology for the three cases. Commented Mar 23, 2012 at 3:51
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    (Off-topic) Once you have 50 reputation you'll be able to comment everywhere. Until then, you can only comment on your own questions and answers. If someone comments on your answer, you can then use @username to "ping" them and get their attention. More details here.
    – Troyen
    Commented Mar 23, 2012 at 4:35
  • "Presumably the old suffixes required finite verb forms, and were lost when the morphologically finite forms disappeared, replaced by the morphologically non-finite forms that had the same meaning (i.e. -ない)." -- By "required finite verb forms", do you mean to argue that, for example, the negative verb ending ぬ ("attributive/non-finite") was lost along with ず ("predicative/finite") as a sort of package deal?
    – Matt
    Commented Mar 23, 2012 at 4:40
  • Also, if you wouldn't mind, would you expand on/clarify your final sentence? It seems interesting, but I don't understand what you mean.
    – Matt
    Commented Mar 23, 2012 at 4:46

As others have argued, it's pretty much a question of definition. But it seems obvious that in form, there's overlap between i-adjectives and plain verb-negatives.

I'm going to try to be constructive about it by starting a list of forms that exist in either or both of the cases. Please add or comment (or fix my formatting) as you see fit.

○食べない    ○赤い
○食べなく    ○赤く
△食べなくない  ○赤くない
○食べなくはない ○赤くはない
○食べなかった  ○赤かった
○食べなそう   ○赤そう
○食べないで   ×赤いで
×食べなさ    ○赤さ
○食べなすぎ   ○赤すぎ

The correspondence seems pretty good to me. And the slight problem with なくない, I consider inherited from ない, since 無くない itself is considered wrong by some.

  • Could the problem with 食べなさ be inherited from ない as well? I was under the impression that -さ, -み, and -め can't attach to the adjective ない. I've been trying to figure this out, and it seems to me like maybe the main difference between 助動詞「ない」 and 形容詞「無い」 is that the latter can't appear in ないで.
    – user1478
    Commented Nov 2, 2013 at 17:11
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    @snailboat, interesting observations. 無さ definitely exists. み is not fully productive for い-adjectives either (e.g. *早み doesn't exist), so not sure 無い is a special case. I think you might be right about め.
    – dainichi
    Commented Nov 3, 2013 at 8:58

No, they aren't adjectives.

They mostly follow the same basic grammatical rules (with a few exceptions) that い adjectives do.

However there are several grammatical constructs that only work with either ~ない verbs or い adjectives.

More over in classical Japanese ~ない was things like ~ず ~ぬ ~ん most of the time. Those constructs have zero resemblance to い adjectives. So anyone attempting to argue that ~ない is effectively an adjective would have to argue that negative verbs became adjectives only in modern times.

Most importantly Japanese text books clearly classify them differently.  動詞の否定形 and い形容詞.

In addition ~ません has very little relevance to this question because ~ます is less of a verb form and more correctly the continuative(い ending) form of a verb + an irregular verb.

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    1. Classical Japanese is irrelevant. The question is about present Japanese. 2. ず, ぬ are at most suppletions of ない (even if you consider them to belong to a single paradigm with ない). Their existence does not negate the fact that ない is an i-adjective. The fact that the English be in 3sg form is is not 1sg am or 2sg are plus -s does not mean that they are not verbs. 3. Just because Japanese textbooks say so is not a valid reason to claim something. Especially, if you are mentioning traditional ones, it is totally unacceptable from a modern view. 4.I thinkthere is no such thing as 意形容詞.
    – user458
    Commented Feb 21, 2012 at 4:21
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    "So anyone attempting to argue that ~ない is effectively an adjective would have to argue that negative verbs became adjectives only in modern times." -- Well... yeah, that's exactly what happened (well, for pre-Edo values of "modern"). Probably because an existing adjective (nai) gradually came to be used as a suffix (-nai), although this explanation is still a bit controversial because the early stages of the change apparently took place without anyone writing them down.
    – Matt
    Commented Feb 21, 2012 at 5:10
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    What do you mean by "However there are several grammatical constructs that only with either ~ない verbs or い adjectives". Can you elaborate/exemplify?
    – dainichi
    Commented Feb 21, 2012 at 5:24
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    @sawa, I had trouble parsing it as well, but I believe Ian is saying that some forms only exist with verb-negatives and/or some forms only exist with i-adjectives. The only thing I can think of are constructs like 食べなくない, which exist, although strictly speaking they might be considered incorrect. Hence, I would like Ian to elaborate.
    – dainichi
    Commented Feb 21, 2012 at 6:50
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    @Ian I don't those are considered productive, are they? I haven't heard 赤げ or 赤がる either. Also, missing forms is usually not enough to expell a word from a word class. ある doesn't have a non-polite negative, but is still a verb.
    – dainichi
    Commented Feb 26, 2012 at 17:02

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