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To be (copula)
Definition
The copula 'です / だ' is used to connect a subject to a predicate, stating identity or description. It is a fundamental part of Japanese grammar, used to link a subject to a state or condition. In formal speech and writing, the polite form 'です' is used, while in informal contexts, the plain form 'だ' is used. This pattern is essential for expressing identity, description, and existence in Japanese.
Structure
| Form | Pattern | Example |
|---|---|---|
| Plain form | Subject + だ + Predicate | 私は学生だ。 (I am a student.) |
| Polite form | Subject + です + Predicate | 私は学生です。 (I am a student.) |
| Negative form | Subject + ではない / ではありません + Predicate | 私は学生ではありません。 (I am not a student.) |
Examples
田中さんは先生です。
Tanaka-san wa sensei desu.
Mr. Tanaka is a teacher.
田中さんは (Mr. Tanaka) + は (topic marker) + 先生です (is a teacher)
これは私の本です。
Kore wa watashi no hon desu.
This is my book.
これは (this) + は (topic marker) + 私の本です (is my book)
明日は日曜日です。
Ashita wa nichiyōbi desu.
Tomorrow is Sunday.
明日は (tomorrow) + は (topic marker) + 日曜日です (is Sunday)
彼は学生だ。
Kare wa gakusei da.
He is a student.
彼は (he) + は (topic marker) + 学生だ (is a student)
Context
The copula 'です / だ' is used to connect a subject to a predicate, stating identity or description. In formal speech and writing, the polite form 'です' is used, while in informal contexts, the plain form 'だ' is used. This pattern is essential for expressing identity, description, and existence in Japanese.
Watch out
In formal speech and writing, 'です' is used to show respect and politeness, while 'だ' is used in informal contexts.
For example, '楽しいだ' is incorrect, while '楽しい' is correct.
For example, '本はあります' (there is a book), while 'これは私の本です' (this is my book)
Strategy
Pay attention to the context and register when using 'です / だ'. In formal speech and writing, use 'です', while in informal contexts, use 'だ'. Be careful not to confuse 'です' with 'ある / いる' for expressing existence.
In context
Worked examples drawn from JLPT N5 test-style questions. Each sentence shows です / だ used correctly, with a brief note on what the pattern is doing.
田中さんは先生です。
Pattern used: です
です connects the topic 田中さん to the predicate 先生, identifying that Tanaka-san is a teacher. ある/いる express existence, not identity.
これは私の本です。
Pattern used: です
In a polite sentence (using は), です is the appropriate copula. だ would be too casual for this sentence style.
明日は日曜日です。
Pattern used: です
The sentence states a present fact about tomorrow being Sunday. です (present polite) is correct. でした is past tense, and ではない is negative.
Interactive
田中さんは先生______。
Adaptive practice
Our adaptive engine will quiz you on this grammar pattern and track your progress toward mastery.