The ない-form is the plain negative of a verb, and it is the base of three patterns you will use constantly at work in Japan.
Building it
| Group | Rule | Example |
|---|---|---|
| 2 (る-verbs) | drop ます, add ない | たべます → たべない |
| 1 (う-verbs) | change the い-row to the あ-row, add ない | のみます → のまない |
| Irregular | - | します → しない, きます → こない |
Two things that catch people:
- Verbs ending in います become わない, not あない: かいます → かわない, いいます → いわない.
- あります is irregular in the negative: it becomes ない (or ありません), not あらない.
If the groups are not clear, this will feel arbitrary: Japanese verb groups.
The three patterns
1. ～ないでください - please do not
ここに 入らないで ください。- Please do not enter here. わすれないで ください。- Please do not forget.
You will meet this on signs and hear it in instructions every day.
2. ～なくてもいいです - you do not have to
けいけんは なくても いいです。- You do not need experience.
This one appears constantly in job advertisements and is a standard reading trap: it applies to one condition only, and candidates read it as applying to all of them. How to read a Japanese notice.
3. ～なければなりません - you must
Built from the ない-form: たべない → たべなければなりません.
The colloquial short forms - ～なきゃ, ～ないと - mean the same thing and are what you will actually hear spoken.
The pair that decides questions
Compare:
- 持ってこなくてもいいです - you do not have to bring it
- 持ってきてはいけません - you must not bring it
One says optional, the other says forbidden, and they look similar to a learner under time pressure. Exams exploit this pair specifically, and in a workplace the difference matters more than a mark.
Also useful
～ないで - without doing: 朝ごはんを 食べないで 来ました。(I came without eating breakfast.)
～なくて - a negative reason: わからなくて、こまりました。(I did not understand, so I was troubled.)
Practise by writing rules
The fastest way to fix these is to write the rules of your own workplace or home in Japanese:
ここで たばこを すわないで ください。 土曜日は 来なくても いいです。 月曜日までに 出さなければ なりません。
Three sentences a day for a week and the forms stop needing calculation. Then check them under pressure with the free practice test, which explains each answer in your own language.