Verb To Be だ and です in Japanese
To study this grammar point, please make sure you understand the following:
Unlike English, Japanese makes no distinction for the choice of verb to be (am, are, is) between first-person, second-person and third-person subjects.
Nonetheless, Japanese grammar distinguishes between plain (casual) form and polite form by either the choice of words, or the modified form of the words.
The plain form for is, am, are in Japanese is だ. The polite form, which is more common in introductory textbooks, is です.
However, the plain form だ and its modified forms are way more important for Japanese grammar, and students should understand their usages.
The plain form verb to be だ and its modified forms are very important in understanding Japanese grammar.
Summary for Japanese Verb To Be (Present, Past, Present Negative)
|is, am, are||was, were||is not, am not, are not|
|Polite Form||です||でした||じゃないです or ではありません|
Is, Am, Are (Present Tense)
- plain form: だ
- polite form: です
Recall that the subject of a sentence can be omitted (if it is understood by the context), and verb is always at the end of a Japanese sentence.
Notice that 学生 (student) is a noun in the sentence. For adjective in such a sentence, such as I am fine, the rules are slightly different. You can learn it from sections for い-adjectives and な-adjectives.
You can also use a noun without any verb to be. It is still a good sentence.
Was, Were (Past Tense)
- plain form: だった
- polite form: でした
Is Not, Am Not, Are Not (Present Negative)
- plain form: じゃない
- polite form: じゃないです or ではありません
Notice that じゃないです is the more common spoken form, and ではありません /dewa-arimasen/ is more formal form for the written format.
Was Not, Were Not (Past Negative)
It is the same rules to derive the past-negative form for い-adjectives (because the suffix ない can be considered as an い-adjective).