Basics
The verb です (desu) is the Japanese word for “to be”:
あれは犬です
あれは いぬです
That is a dog.
私は田中です
わたしは たなかです
I am Tanaka.
モチは私のお気に入りです
モチは わたしの おきにいりです
Mochi is my favorite.
Like all Japanese verbs, です (desu) is placed at the end of the clause it belongs to. If the sentence with です (desu) is made up of a single clause, then です (desu) goes at the end of the sentence.
The plain form of です (desu) is だ (da). This is the form used in informal speech:
あれは犬だ
あれは いぬだ
That is a dog.
私は田中だ
わたしは たなかだ
I am Tanaka.
モチは私のお気に入りだ
モチは わたしの おきにいりだ
Mochi is my favorite.
Outside of changing the politeness of the sentence, using だ (da) instead of です (desu) does not change the meaning of the sentence.
The verb です (desu) is also called “the copula.” This is because, like in many other languages, the verb “to be” couples two elements together by creating an equals relationship between the two. In English, “to be” (along with other verbs) is called a “linking verb” because it links two elements together.
Let’s look at an example that clearly illustrates this linking effect:
私は人間です
わたしは にんげんです
I am human.
In the above example, we can see in both Japanese and English how the verb “to be” links two elements (a pronoun and a noun) into an equality relationship:
私＝人間
わたし＝にんげん
I = human
This linking or coupling effect is the reason why です (desu) is called “the Japanese copula.”
Complex sentences
The copula です (desu) can of course be used in sentences with more than one clause (complex sentences).
Let’s look at some examples:
それを言ったのは山田です
それを いったのは やまだです
The one who said that is Yamada. / Yamada is the one who said that.
私が買ったのはリンゴだ
わたしが かったのは リンゴだ
What I bought were apples. / Apples are what I bought.
それに気づいたのは彼女だ
それに きづいたのは かのじょだ
The one who noticed that is her. / She is the one who noticed that.
In all the above examples, we have the following pattern:
[clause]のは[noun/pronoun]です/だ
When placed after a clause (i.e., after a verb), the particle の (no) turns the preceding clause into a noun phrase. Since such a clause now works like a noun, adding the particle は (wa) after it turns it into the topic of the sentence.
In our example sentences, the addition of のは (no wa) after the clauses at the start of the sentence creates the following phrases:
それを言ったのは
それを いったのは
The one who said that
私が買ったのは
わたしが かったのは
What I bought
それに気づいたのは
それに きづいたのは
The one who noticed that
Since we now have noun clauses marked by the topic particle は (wa), these clauses can now be used with the copula です (desu) to link them to other elements.
In the first example, we link the clause with 山田 (Yamada), a proper noun:
それを言ったのは山田です
それを いったのは やまだです
The one who said that is Yamada. / Yamada is the one who said that.
In the second example, we link the clause with リンゴ (ringo), a common noun:
私が買ったのはリンゴだ
わたしが かったのは リンゴだ
What I bought were apples. / Apples are what I bought.
Finally, in the third example, we link the clause to 彼女 (kanojo), a personal pronoun:
それに気づいたのは彼女だ
それに きづいたのは かのじょだ
The one who noticed that is her. / She is the one who noticed that.
As we can see, the pattern
[clause]のは[noun/pronoun]です/だ
is very common and very useful in Japanese, so it’s great to learn it from an early stage.
Advanced topic – The copula in relative clauses
Let’s look at the following English sentences:
My teacher Tanaka is very strict.
I, the boss, will choose.
You, who are the hero of legend, shall save the kingdom.
In all the above sentences, the copula appears in a clause that is not the main one. In the first and second sentences, the copula doesn’t appear explicitly, but it is present implicitly.
Let’s look at the sentences again, but with the implied copula made explicit in the first two:
My teacher, (who is) Tanaka, is very strict.
I, (who am) the boss, will choose.
You, who are the hero of legend, shall save the kingdom.
In order to render these sentences into Japanese, we’ll need to use the copula in a relative clause, rather than in the main clause. To do that, we’ll need to use a different form of the copula.
The form です (desu) of the copula is actually a shorthand of a another form of the copula.
That other form looks like this:
である (de aru)
Yes, that ある (aru) is the verb of existence ある (aru).
This form of the copula explains why the negative of the copula is ではありません (de wa arimasen) or ではない (de wa nai): these negative forms simply negate あります (arimasu) or ある (aru) and add は (wa) for emphasis.
Let’s look at our example sentences and isolate the relative clauses that contain the copula, along with the noun that the relative clauses modify:
My teacher, (who is) Tanaka
I, (who am) the boss
You, who are the hero of legend
To express these relative clauses in Japanese, we employ である (de aru) as follows:
My teacher, (who is) Tanaka
私の先生である田中
わたしの せんせいである たなか
I, (who am) the boss
ボスである私
ボスである わたし
You, who are the hero of legend
伝説の勇者である貴方
でんせつの ゆうしゃである あなた
Now that we’ve created these noun phrases with relative clauses, we can treat them as any noun. We can place は (wa) after them to make them into the topic of the sentence and finally add the predicate:
My teacher, (who is) Tanaka, is very strict.
私の先生である田中はとても厳しい
わたしの せんせいである たなかは とても きびしい
I, (who am) the boss, will choose.
ボスである私は選ぶ
ボスである わたしは えらぶ
You, who are the hero of legend, shall save the kingdom.
伝説の勇者である貴方は王国を救います
でんせつの ゆうしゃである あなたは おうこくを すくいます
Thus, the である (de aru) form of です (desu) allows employing the Japanese copula in relative clauses.
By the way, since the ある (aru) in である (de aru) is the existence verb, that means that ござる (gozaru) /ございます (gozaimasu), the super-polite form of ある (aru), can be used in the copula as well.
This is commonly done in fiction, especially with characters that are meant to evoke a very old-fashioned Japanese-ness. A notable example of such a character is Shishigami Bang from the BlazBlue series, who always uses でござる (de gozaru) for his copulas.
Bang might say things like:
そうでござる！ (instead of そうです)
結構でござる！
けっこうでござる！ (instead of けっこうです)
面白いでござる！
おもしろいでござる！ (instead of おもしろいです)
This way of speaking sounds exaggerated even to native Japanese speakers, and is meant to characterize Shishigami Bang as eccentric, funny, and extremely old-fashioned.
Conclusion
The Japanese copula です (desu) is the fundamental building block of Japanese sentences. It can be used to create the most basic sentences as well as complex ones.
The copula has various forms that are used for different purposes, including uses in fiction, where it can be used to give a particular flavor to a story’s characters.
