The Nai-Form

Japanese Grammar 2

Course 2 · Chapter 5 · The ない-Form

🚫 The ない-Form — ない-けい

The ない-form (ないけい, also called the plain negative) is the second great building block after the te-form. It is the plain way to say "doesn't / won't do", and it is the base for prohibitions, "don't have to" and "must". You already know how to find the ない-stem (Chapter 1); now you use it.

1. Forming the ない-form

The ない-form is an い-adjective

ない inflects exactly like an い-adjective, which gives you the whole plain negative system:

2. 〜ないでください: please don't

The ない-form + でください asks someone not to do something. (You can also write 〜ないで alone to a friend.)

This is softer and more courteous than 〜てはいけません (Chapter 4), and is the one to use with strangers.

3. 〜なくてもいいです: don't have to

The negative te-form (〜なくて) + もいいです: it is fine not to do it.

4. 〜なければなりません: must

Japanese expresses obligation by a double negative: 〜なければ ("if you don't ...") + なりません ("it won't do"): "If you don't do it, it won't do", that is, "you must".

5. 〜ないほうがいい: had better not

The ない-form + ほうがいいです gives advice: "it would be better not to". Its positive partner uses the past plain form (〜たほうがいい, Chapter 6).

A related, useful form: 〜ないで also means "without doing": あさごはんを たべないで いきました。 ("I left without eating breakfast.")

🗣️ In Use — つかいかた

The ない-form in everyday talk.

📋 Quick Reference

✍️ Practice — れんしゅう

Try each one, then click to check.