です vs だ in Japanese
The polite です and the plain だ: what they mean, their past and negative forms, and when to use each.
- Polite
- です (desu)
- Plain
- だ (da)
- Past
- でした / だった
- Never
- たかいだ (い-adjective + だ)
Same meaning, different politeness
がくせいです。(Gakusei desu.) I'm a student. Polite.
がくせいだ。(Gakusei da.) I'm a student. Plain.
Use です with people you don't know well, at work, and with anyone older than you. Use だ with close friends and family. As a beginner, use です by default.
The four basic forms
Present: です / だ. がくせいです / がくせいだ.
Negative: じゃありません or じゃないです / じゃない. がくせいじゃありません / がくせいじゃない. じゃ is the spoken contraction of では, so ではありません sounds more formal.
Past: でした / だった. がくせいでした / がくせいだった.
Past negative: じゃありませんでした or じゃなかったです / じゃなかった.
With adjectives
な-adjectives work like nouns: しずかです / しずかだ (it's quiet), しずかでした / しずかだった (it was quiet).
い-adjectives are different. たかいです (it's expensive) is polite, but the plain form is just たかい. たかいだ is wrong.
い-adjectives also change their own ending for the past: たかかったです, not たかいでした.
When だ drops out
Casual questions usually leave だ out: げんき？ (Genki?) Are you well?
Casual answers often leave it out too: うん、げんき。(Un, genki.) Yeah, I'm fine.
In writing
News, essays and many books use the plain style, with だ or the more formal である.
Emails, letters and anything addressed to a stranger use です.
Related reading
- Japanese grammar overview
- Japanese adjective conjugation
- The masu form
- Japanese sentence structure
- I-adjectives and na-adjectives
- Keigo: Japanese politeness
Common questions
Is だ rude?+
Not rude, but casual. With a stranger, a teacher or a customer it can sound too familiar.
What do でしょう and だろう mean?+
Probably. あしたはあめでしょう (ashita wa ame deshō) means it will probably rain tomorrow. でしょう is polite and だろう is plain.
Is です a verb?+
It works like one at the end of a sentence. Grammars call it a copula: it links a topic to what it is.
Should I study plain or polite first?+
Polite first. Most textbooks and Inku's lessons start with です and ます, because they are safe with everyone.
