Now I have seen people call だ the only copula, even excluding its adverbial or attributive forms で and な (and seemingly の), with the argument that only predicative copulas, which are necessary for predicative expressions, can be called "copula".

Others include them in the term "copula" and simply differentiate between "Conclusive" and "Adnominal".

However I have not found a discussion on this site about the suffix that follows the stem of adjectives in their 終止形, well, predicative form. It seems to me, that this suffix, which can be inflected, works like a copula.

Some claim that in ...が綺麗(です) and ...が可愛い, there is a predication in both, but in the second case, い is responsible, not any ommitted です, for which to use we would have to nominalise the expression anyways: ...が可愛いのです/だ, although です has sort of been accepted to use behind an adjective despite being technically incorrect. In short: ~い = "to be"?

However, some things make me question this: A sentence doesn't need a copula(call it a verb or not) OR verb to be grammatically correct, meaning, an adjective in its 終止形 form is a whole sentence. But we cannot ommit the suffix.

But then again, attributively, we inflect い and don't add any だ-variant. This argument depends on whether you think attributive versions of だ are even "true" copula.

So, I am conflicted. Could you call い some kind of copula? Maybe a suffix with copulative properties?

Any linking to a question which already answered this would be helpful, too.

1 Answer 1


Could you call the い/i - suffix of adjectives a copula?

The short answer


The longer answer

A "copula" is an independent word used to link a subject with its predicate, in an "X is Y" kind of relationship.

In Japanese, だ・です does this: it is an independent word, that explicitly states that something is.

The ~い ending of an ''-i'' adjective, however, doesn't do this: it is not an independent word, and it doesn't state that something is in general terms, so much as that something is the specific quality of that adjective.

The ~い ending has predicative and attributive functions, but it is not a copula.

  • Interesting, some sites on the internet claim that い does explicitly state that something is, and therefore, is a "sort-of" copula, some kind of suffix that has some properties of copula but some not, like you mention, not being an indepentent word. I wonder how they got that idea and where they got it from, because I still like the idea of thinking of い that way. It's sad but good to learn the truth Nov 23, 2022 at 1:53
  • Then would you not agree in calling attributive and adverbial versions of だ (de, na, no) a "copula". I have linked a stackexchange post in my answer that is about that topic. But I still find both opinions online. What is your opinion? Nov 23, 2022 at 1:57
  • @OranMatheus, if we define "copula" as "an independent word", then で and な and の, as particles, could meet that definition. 😄 Since ~い is not "an independent word", and also because it is tied exclusively to a specific word class, it does not meet the definition for a "copula". Nov 23, 2022 at 17:46
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    The ~い ending is predicative, in that an -i adjective can be used to end a sentence in a fully grammatical way. That might be what has some people confused about its "copula-ness". However, a copula can be used to state that "X is [pretty much anything]", or even just "X is", while the ~い ending only attaches to that class of adjective (it's basically a suffix), and only means "X is [this specific quality]" -- it cannot be used to mean "X is [anything]" or just plain "X is". Nov 23, 2022 at 17:54
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    IMHO, better than trying to jump through hoops to call a suffix a copula, etc, I've always thought it much more reasonable to simply consider い-adjectives to be not really adjectives at all, but essentially just another class of verb (which have a few limitations on how they can be conjugated compared to other verbs). I think this much more closely reflects how they actually function in the language. (It's important to understand that in matters like this, there's really no "right" or "wrong" answer, it's just a question of which way of looking at things is the most useful for other things)
    – Foogod
    Nov 23, 2022 at 18:52

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