copula N5 essential casualwritten
だ — plain non-past copula 'is / are'
だ
Meaning
- is / are — equates the topic with a noun or na-adjective (the plain-form copula)
だ is blunt and assertive. In relaxed speech it is often dropped entirely (これ、誰の？) and sounds masculine when kept at the end of a statement, so everyday conversation frequently leaves it off or softens it to だよ・だね.
Key sentence
これは本だ。
This is a book.
Formation
| Attaches to | Form | Example |
|---|---|---|
| Noun | N + だ | 学生だ |
| na-adjective | stem + だ | 静かだ |
When: Plain/casual register. The polite equivalent is です; the written/formal equivalent is である.
Examples
彼は医者だ。
He is a doctor.
今日は休みだ。
Today is a day off.
ここが入口だ。
This is the entrance.
それは秘密だ。
That's a secret.
When you can't use it
- だ never attaches to verbs or i-adjectives — they are already complete predicates (×行くだ, ×高いだ). It joins only to nouns and na-adjectives.
Easily confused with
See だ in real sentences
Jengo shows だ the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.
Study it in JengoSources Compiled with reference to A Dictionary of Basic Japanese Grammar, A Dictionary of Intermediate Japanese Grammar.