Translation guide
In Japanese, the copula links a subject to a noun or adjectival noun predicate, expressing 'is', 'am', 'are', etc. The most common copula is だ (plain) / です (polite). Unlike English, the copula is not used with i‑adjectives, and it changes form for tense, negation, and politeness. This guide covers the core copula forms and their uses.
Expressing 'X is Y' in the present or future tense, where Y is a noun or na‑adjective.
Polite copula used in formal and everyday polite speech. Attaches directly to nouns and na‑adjective stems.
This is a pen.
彼は学生です。
He is a student.
Plain (casual) copula used in informal speech, written language, and relative clauses. Often dropped in casual feminine speech.
Very formal/humble copula, used in keigo (honorific/humble speech). Often heard in service encounters.
こちらが会議室でございます。
This is the conference room.
In very casual conversation, especially among close friends or in feminine speech, the copula だ is often dropped. です is not dropped.
これ、ペン。
This is a pen. (casual)
Expressing 'X is not Y' in the present or future tense.
Polite negative form of です. In speech, often contracted to じゃありません.
これは本ではありません。
This is not a book.
それは簡単じゃありません。
That is not easy.
Less formal negative, common in everyday polite speech. Combines じゃない (plain negative) with です.
これは本じゃないです。
This is not a book.
Plain negative copula. In speech, often contracted to じゃない.
これは本ではない。
This is not a book.
それは簡単じゃない。
That is not easy.
Very formal negative copula, humble form.
こちらは会議室ではございません。
This is not the conference room.
Expressing 'X was Y'.
Polite past form of です.
昨日は月曜日でした。
Yesterday was Monday.
Plain past form of だ.
昨日は月曜日だった。
Yesterday was Monday.
Very formal past copula.
先日はお世話になりました。こちらは社長でございました。
Thank you for the other day. This was the president.
Expressing 'X was not Y'.
Polite past negative. Often contracted to じゃありませんでした in speech.
それは真実ではありませんでした。
That was not the truth.
Less formal past negative, common in everyday polite speech.
それは真実じゃなかったです。
That was not the truth.
Plain past negative. Often contracted to じゃなかった.
それは真実ではなかった。
That was not the truth.
Linking clauses or making requests with the copula.
The te-form of the copula, used to connect clauses ('and'), indicate reason, or form polite requests with ください.
彼は学生で、私は先生です。
He is a student, and I am a teacher.
静かでいいですね。
It's quiet, which is nice.
Formal/literary conjunctive form, often used in writing.
彼は学者であり、詩人でもある。
He is a scholar and also a poet.
Expressing 'let it be' or 'probably is'.
Polite tentative form, used for probability ('probably is') or seeking agreement. In casual speech, だろう is used.
明日は雨でしょう。
It will probably rain tomorrow.
Plain tentative form, used in casual speech and writing for conjecture or rhetorical questions.
彼は来ないだろう。
He probably won't come.
Expressing 'if it is'.
Conditional form of the copula, meaning 'if it is'. Often shortened to なら in speech.
学生であれば、割引があります。
If you are a student, there is a discount.
Common conditional form derived from だ, used for contextual assumptions ('if it is the case that').
彼が来るなら、私も行く。
If he is coming, I'll go too.
Understanding that i-adjectives do not take だ/です in the present affirmative, but do in other forms.
I-adjectives inherently contain the copula meaning. Adding だ is ungrammatical. です can be added for politeness but is not a copula; it's a politeness marker.
Never say 面白いだ. It is incorrect.
この本は面白い。
This book is interesting.
この本は面白いです。
This book is interesting. (polite)
Past tense of i-adjectives, which replaces the copula function.
昨日は寒かった。
Yesterday was cold.
In present affirmative, i-adjectives like おいしい (delicious) already mean 'is delicious'. Adding だ (おいしいだ) is a common learner mistake. Use おいしい (plain) or おいしいです (polite).
このラーメンはおいしい。
This ramen is delicious.
だ is the plain form used in casual speech, written language, and relative clauses. です is the polite form used in formal and everyday polite conversation. Using だ in polite contexts can sound rude.
これは本だ。 (casual)
This is a book.
これは本です。 (polite)
This is a book.
In very informal conversation, especially among women, だ is often dropped. です is never dropped. This can make speech sound softer.
これ、何？
What's this?