How to Express Prohibition and Obligation: だめだ, いけない, and ならない

Last time, you learned how to make commands and requests, e.g. “もっと勉べん強きょうしろ (Study more),” “もっと勉べん強きょうしてくれませんか (Could you please study more)？” Then, if you would like to say, “you have to study more,” what should you do? In this lesson, you will learn how to express obligation and prohibition.

Explanation for How to Express Prohibition and Obligation

Obligation means “what you must do” while prohibition means “what you must not do.” They are generally determined by law, contracts, customs, common sense, etc. In English, you can express them by placing a key phrase such as “must” or ”have to” before a verb. In Japanese, you express obligation and prohibition by conjugating verbs.

Basic Idea of だめだ, いけない, and ならない

ボブはもっと 勉べん強きょうしなければ | だめだ
ボブはもっと 勉べん強きょうしなければ | いけない
ボブはもっと 勉べん強きょうしなければ | ならない

All of the examples above mean “Bob must study more.” The difference is the formality, i.e. だめだ is casual and mostly used in conversation, いけない is neutral, and ならない is formal and used in writing. As you can see, we have divided the conditional verb part, i.e. 勉強しなければ from the second part in bold. You can also replace the conditional verb with several words in order to express different formality. You will learn the words one by one here. First of all, please memorize the concept of the three words: だめだ, いけない, and ならない (*You will learn Japanese conditionals in detail in other lessons).

Prohibition: …ては + だめだ・いけない・ならない

The conjugation is simple. You can utilize the te-form and attach は. Then, you choose one of the three words depending on the context. If you use sentence-ending particles, your speech will sound softer.

The above sentences sound formal even if you use だめだ. If you would like to be more casual, you can replace では with じゃ and ては with ちゃ. In this context, ならない is not suitable.

Obligation: なければ + だめだ・いけない・ならない

The conjugation is also simple. You can utilize the negative form. You just replace ない (of the negative form) with なければ. Just like the above, by using sentence-ending particles, you can make your speech softer.

なければ actually sounds really formal and is rarely used in conversation. By replacing なければ with なきゃ, you can make your speech more suitable for conversation. In this context, だめだ or いけない should be used.

If you would like to more casual, you can drop the part after なきゃ.

Alternative Sentence Patterns

You know one sentence pattern when it comes to expressing obligation, however, there are still two other patterns. The meanings are almost the same. Thus, please pay attention to the formality.

なくては / なくちゃ + だめだ・いけない・ならない

The conjugation is the same as the first sentence pattern. Instead of なければ, you replace ない (of the negative form) with なくては. Then, by replace ては with ちゃ, you can make your speech more casual. In that case, ならない is not suitable because of its high formality.

You can also leave out the part after ちゃ to be more casual.

ないと + だめだ・いけない

Since the formality is lower than the other sentence patterns, ならない cannot be used with ないと. The conjugation is just to attach と to the negative form. This sounds neutral, which allows you to use this in both speaking and writing.

You can drop the part after ないと just like other sentence patterns.

Summary

The three sentence patterns in the expressions of obligation may be a little tricky. Since the meanings are the same, you can use your preferred one. Thus, it is alright if you can just recognize them when native speakers use them with you. Now you can express prohibition and obligation. Next you will learn how to express permission and advice.