GrammarJLPT N5
→ be
The Copula (to be)
JLPT N5CopulaNeutral
だ and です are the Japanese copula, equivalent to the English verb "to be" (is, am, are). They connect a subject to a noun or a な-adjective predicate, asserting that something is something else. だ is the plain (casual) form and です is the polite form. Unlike English "to be," the Japanese copula does not appear with い-adjectives in standard modern grammar — い-adjectives already contain the predicate function within themselves, so adding だ directly to an い-adjective is grammatically incorrect (though です is added after い-adjectives purely for politeness, which is a special exception). The copula is placed at the end of a sentence or clause, following Japanese word order. In casual speech, だ is sometimes dropped entirely, especially by female speakers or in questions. The negative forms are じゃない (casual) and ではありません or じゃありません (polite), and the past forms are だった (casual) and でした (polite). Learners should note that だ and です are not simply interchangeable — choosing between them signals your level of politeness and social awareness, making this one of the most fundamental choices in Japanese communication.
Functions
#1 Identifying or equating (Noun sentences)
Structure
A は B だ / です
これは本です。
Here です links the subject これ (this) to the noun 本 (book), stating that they are the same thing. This is the most basic use of the copula — identification. In casual speech, you could say これは本だ to convey the same meaning with a plain tone. The particle は marks the topic, and the copula comes at the very end of the sentence, which is standard Japanese sentence structure.This is a book.
Structures
- Noun
- Noun + だ (casual) / です (polite)
- な-Adjective
- な-Adjective stem + だ (casual) / です (polite)
Common mistakes
One of the most common errors is attaching だ directly to い-adjectives, such as saying 大きいだ, which is incorrect — い-adjectives already function as predicates on their own, so the correct forms are 大きい (casual) or 大きいです (polite, where です is added only for politeness). Another frequent mistake is using だ at the end of a polite sentence or mixing だ and です within the same conversation inconsistently, which sounds unnatural. Learners also sometimes add だ before the question particle か in casual speech (本だか?), but casual questions typically drop だ and just use a rising intonation (本？ or 本なの？). Finally, beginners may forget that だ and です are only used with nouns and な-adjectives as predicates, not with verbs — saying 食べるです is incorrect; the polite verb form 食べます should be used instead.
Related
であるじゃないではありませんだったでしたでございます