One of the trickiest part of Japanese is that there is no verb for the state-of-being like the verb "to be" in English. You can, however, declare what something is by attaching the Hiragana character 「だ」 to a noun or na-adjective only. (We will learn about na-adjectives in the section on adjectives later.)
Seems easy enough. Here's the real kicker though.
You can say you're doing well or someone is a student without using 「だ」 at all. For example, below is an example of a very typical greeting among friends. Also notice how the subject isn't even specified when it's obvious from the context.
Ａ：元気？
A: (Are you) well?
Ｂ：元気。
B: (I'm) well.
So you may be wondering, "What's the point of using 「だ」?" Well, the main difference is that a declarative statement makes the sentence sound more emphatic and forceful in order to make it more... well declarative. Therefore, it is more common to hear men use 「だ」 at the end of sentences.
The declarative 「だ」 is also needed in various grammatical structures where a state-of-being must be explicitly declared. There are also times when you cannot attach it. It's all quite a pain in the butt really but you don't have to worry about it yet.
In Japanese, negative and past tense are all expressed by conjugation. We can conjugate a noun or adjective to either its negative or past tense to say that something is not [X] or that something was [X]. This may be a bit hard to grasp at first but none of these state-of-being conjugations make anything declarative like 「だ」 does. We'll learn how to make these tenses declarative by attaching 「だ」 to the end of the sentence in a later lesson.
First, for the negative, attach 「じゃない」 to the noun or na-adjective.
We will now learn the past tense of the state-of-being. To say something was something, attach 「だった」 to the noun or na-adjective.
In order to say the negative past (was not), conjugate the negative to the negative past tense by dropping the 「い」 from 「じゃない」 and adding 「かった」.
Example: 友達＋だった ＝友達だった
We've now learned how to express state-of-being in all four tenses. Next we will learn some particles, which will allow us assign roles to words. Here is a summary chart of the conjugations we learned in this section.
| Positive | Negative | |||
|---|---|---|---|---|
| Non-Past | 学生（だ） | Is student | 学生じゃない | Is not student |
| Past | 学生だった | Was student | 学生じゃなかった | Was not student |
In the following exercises, we will practice the state-of-being conjugations we just covered. But first, you might want to learn or review the following useful nouns that will be used in the exercises.
We are now going to practice the state-of-being conjugations in order. Take each noun and conjugate it to the following forms: the declarative, negative state-of-being, past state-of-being, and negative past state-of-being.
Sample: 人 ＝ 人だ、人じゃない、人だった、人じゃなかった
| declarative | = | これだ |
| negative | = | これじゃない |
| past | = | これだった |
| negative-past | = | これじゃなかった |
| declarative | = | 大人だ |
| negative | = | 大人じゃない |
| past | = | 大人だった |
| negative-past | = | 大人じゃなかった |
| declarative | = | 学校だ |
| negative | = | 学校じゃない |
| past | = | 学校だった |
| negative-past | = | 学校じゃなかった |
| declarative | = | 友達だ |
| negative | = | 友達じゃない |
| past | = | 友達だった |
| negative-past | = | 友達じゃなかった |
| declarative | = | 学生だ |
| negative | = | 学生じゃない |
| past | = | 学生だった |
| negative-past | = | 学生じゃなかった |
In this second exercise, we are really going to test your conjugation knowledge as well as the vocabulary by translating some simple English sentences.
Please note that while the positive, non-past state-of-being can be implied, for the purpose of this exercise, we will assume it's always declaratory. Don't forget that
this creates a very firm and declaratory tone.
Sample: Is student. ＝ 学生だ。
| 1. Is college. | ＝ | 大学だ。 |
| 2. Is not high school. | ＝ | 高校じゃない。 |
| 3. Was teacher. | ＝ | 先生だった。 |
| 4. Is adult. | ＝ | 大人だ。 |
| 5. Was not child. | ＝ | 子供じゃなかった。 |
| 6. This was the way it was. | ＝ | こうだった。 |
| 7. Wasn't that over there. | ＝ | あれじゃなかった。 |
| 8. Is not middle school. | ＝ | 中学校じゃない。 |
| 9. Is friend. | ＝ | 友達だ。 |
| 10. Was not car. | ＝ | 車じゃなかった。 |
| 11. Was this. | ＝ | これだった。 |
| 12. That's not the way it is. | ＝ | そうじゃない。 |
In this last exercise, we'll practice answering very simple questions using the state-of-being. The yes or no answer （うん or ううん） will be given and it is your job to complete the sentence. In deciding whether to use the declaratory 「だ」, I've decided to be sexist here and assume all males use the declaratory 「だ」 and all females use the implicit state-of-being (not the case in the real world).
Sample:
Ｑ） 学生？
Ａ） ううん、学生じゃない。
| Ｑ１） 友達？ Ａ１） うん、 。 (female) |
Ｑ１） 友達？ Ａ１） うん、友達。 (female) |
| Ｑ２） 学校？ Ａ２） ううん、 。 |
Ｑ２） 学校？ Ａ２） ううん、学校じゃない。 |
| Ｑ３） それだった？ Ａ３） ううん、 。 |
Ｑ３） それだった？ Ａ３） ううん、それじゃなかった。 |
| Ｑ４） そう？ (Is that so?) Ａ４） うん、 。 (male) |
Ｑ４） そう？ (Is that so?) Ａ４） うん、そうだ。 (male) |
| Ｑ５） これ？ Ａ５） ううん、 。 (object is away from the speaker) |
Ｑ５） これ？ Ａ５） ううん、それじゃない。 (object is away from the speaker) |
| Ｑ６） 先生だった？ Ａ６） うん、 。 |
Ｑ６） 先生だった？ Ａ６） うん、先生だった。 |
| Ｑ７） 小学校だった？ Ａ７） ううん、 。 |
Ｑ７） 小学校だった？ Ａ７） ううん、小学校じゃなかった。 |
| Ｑ８） 子供？ Ａ８） うん、 。 (female) |
Ｑ８） 子供？ Ａ８） うん、子供。 (female) |