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.
Plain (casual) copula used in informal speech, written language, and relative clauses. Often dropped in casual feminine speech.
This is a pen.
Very formal/humble copula, used in keigo (honorific/humble speech). Often heard in service encounters.
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.
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.
This is not a book.
Expressing 'X was Y'.
Polite past form of です.
Yesterday was Monday.
Expressing 'X was not Y'.
Polite past negative. Often contracted to じゃありませんでした in speech.
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.
Expressing 'let it be' or 'probably is'.
Expressing 'if it is'.
Conditional form of the copula, meaning 'if it is'. Often shortened to なら in speech.
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.
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).
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.
He is a student.
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.
This is not a book.
Plain negative copula. In speech, often contracted to じゃない.
This is not a book.
That is not easy.
Very formal negative copula, humble form.
This is not the conference room.
Plain past form of だ.
Yesterday was Monday.
Very formal past copula.
Thank you for the other day. This was the president.
Less formal past negative, common in everyday polite speech.
That was not the truth.
Plain past negative. Often contracted to じゃなかった.
That was not the truth.
彼は学生で、私は先生です。
He is a student, and I am a teacher.
It's quiet, which is nice.
Formal/literary conjunctive form, often used in writing.
He is a scholar and also a poet.
It will probably rain tomorrow.
Plain tentative form, used in casual speech and writing for conjecture or rhetorical questions.
He probably won't come.
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').
If he is coming, I'll go too.
This book is interesting.
This book is interesting. (polite)
Past tense of i-adjectives, which replaces the copula function.
Yesterday was cold.
これは本だ。 (casual)
This is a book.
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.
What's this?
It's not a problem.