To ask for permission in Japanese, use the verb in the て form followed by もいいですか: 座ってもいいですか means “May I sit?”. To say that an action is not allowed, the basic pattern is てはいけません or てはだめです. The main difference is between asking if something is allowed and establishing a prohibition.
These constructions depend on the て form of Japanese verbs. Once you know how to form 食べて, 読んで and shite, you can apply the patterns in this guide to many verbs.
Permission and prohibition in Japanese: quick summary
| Function | Structure | Example |
|---|---|---|
| Asking for permission | Vて + もいいですか | 入ってもいいですか |
| Giving permission | Vて + もいいです | 入ってもいいです |
| Politely prohibiting | Vて + はいけません | 入ってはいけません |
| Saying you cannot | Vて + はだめです | 入ってはだめです |
| Casually prohibiting | Vちゃ／Vじゃ + だめ | 入っちゃだめ |
In the table, Vて represents the verb in the て form. The particle は, written with the hiragana は and pronounced wa in this function, participates in prohibition constructions. If this distinction still causes doubt, consult the guide to basic Japanese particles.
How to ask permission with てもいいですか
The most useful formula for beginners is:
verb in the て form + もいいですか
もいいですか adds the idea of “is it okay if I do?” to the verb. The explanation from the Japan Foundation on how to ask permission presents exactly this pattern and shows affirmative and negative responses used in real situations.
ここに座ってもいいですか。
Koko ni suwatte mo ii desu ka?
Can I sit here?
この辞書を使ってもいいですか。
Kono jisho o tsukatte mo ii desu ka?
Can I use this dictionary?
窓を開けてもいいですか。
Mado o akete mo ii desu ka?
Can I open the window?
Since the sentence already ends in ですか, there is no need to add another interrogative particle. The article about how to ask questions in japanese explains the role of か in other types of questions.
Casual and more careful forms
Among friends, it is common to drop ですか and use only てもいい？. In a professional conversation or when asking something delicate, てもいいでしょうか sounds more careful. The material Irodori Elementary 1, from the Japan Foundation, differentiates てもいいですか in てもいいでしょうか in requests for permission at work.
- これ、見てもいい？ — Can I see this? Casual form.
- 少し早く帰ってもいいですか。 — Can I leave a little earlier? Polite form.
- 明日、休んでもいいでしょうか。 — Would it be possible for me to take the day off tomorrow? More careful form.
How to give or deny permission
To authorize an action, you can respond with はい、いいですよ (“Yes, you may”) or どうぞ (“Go ahead”). It is also possible to use the affirmative construction Vてもいいです.
Koko de shashin o totte mo ii desu yo.
Koko de shashin o totte mo ii desu yo.
You can take photos here.
てもかまいません conveys “there is no problem if you do” and can appear in formal contexts:
Kono seki o tsukatte mo kamaimasen.
Kono seki o tsukatte mo kamaimasen.
There is no problem using this seat.
To deny a request without sounding abrupt, responses like Sumimasen, chotto...... or a short explanation can be more natural than a simple いいえ. In rules, notices, and situations that require clarity, however, a direct prohibition is appropriate.
How to prohibit with てはいけません and てはだめです
The basic prohibition structure is:
verb in て form + は + いけません
てはいけません indicates that an action is not allowed. The analysis by the Japan Foundation on instructions, orders, and prohibitions notes that てはいけない is a clear and strong form of prohibition. Therefore, context and the relationship between people matter.
Koko de tabako o sutte wa ikemasen.
Koko de tabako o sutte wa ikemasen.
Smoking is not allowed here.
Kono heya ni haitte wa ikemasen.
Kono heya ni haitte wa ikemasen.
You cannot enter this room.
てはだめです also indicates that something cannot be done. てはなりません is more formal and appears mainly in rules, regulations, and written language.
- 試験中に辞書を使ってはだめです。 — You cannot use a dictionary during the exam.
- ここに車を止めてはなりません。 — It is forbidden to park the car here.
Colloquial contractions: ちゃだめ and じゃだめ
In casual speech, ては can contract to ちゃ, while dewa can become ja. Thus, 食べてはだめ becomes 食べちゃだめ, and 飲んではだめ becomes 飲んじゃだめ.
ここで食べちゃだめ。
Koko de tabecha dame.
You cannot eat here.
この水を飲んじゃだめ。
Kono mizu o nonja dame.
Do not drink this water.
These contractions are natural in conversations, but they can sound strong. With strangers or in customer service, prefer a polite form or explain the reason.
Permission is not the same as ability
Vてもいい deals with permission; Vことができる or the potential form mainly deal with ability or possibility. Compare:
- ここで泳いでもいいです。 — It is allowed to swim here.
- ここで泳ぐことができます。 — It is possible to swim here.
In Portuguese, both sentences can contain “poder”, but the question behind them is different: “do I have permission?” or “is it possible?”. See the full explanation of koto ga dekiru for ability and possibility.
Three differences that prevent mistakes
てはいけません versus ないでください
Vてはいけません states that the action is prohibited. Vないでください asks the person not to do something. The second form is a negative request and can be more appropriate when you are speaking directly to someone. The guide to imperative sentences and requests in Japanese shows other options and their levels of strength.
- ここで写真を撮ってはいけません。 — It is not allowed to take photos here.
- ここで写真を撮らないでください。 — Please do not take photos here.
てはいけません versus なくてもいいです
Vなくてもいいです does not mean “cannot”. It means that it is not necessary to do the action.
- 今日は来なくてもいいです。 — You do not need to come today.
- 今日は来てはいけません。 — You cannot come today.
Do not eliminate も in any context
In speech, you may hear Vていい？ instead of Vてもいい？. For beginners, keeping も helps recognize the structure and avoids extending the omission to contexts where it does not sound natural.
Mini dialogue: asking for permission
A: すみません、ここで写真を撮ってもいいですか。
Sumimasen, koko de shashin o totte mo ii desu ka?
Excuse me, may I take photos here?
B: 申し訳ありません。館内では写真を撮ってはいけません。
Mōshiwake arimasen. Kannai de wa shashin o totte wa ikemasen.
Sorry, taking photos inside the building is not allowed.
The dialogue combines a polite request with a clear prohibition and a brief apology. This pattern works in stores, museums, schools, and other places with their own rules.
Quick exercise
Complete the sentences with the most appropriate option.
- ここに座って（ ）ですか。 — May I sit here?
- この部屋に入っては（ ）。 — You cannot enter this room.
- 明日は来なくても（ ）。 — You don't have to come tomorrow.
- Transform 食べてはだめ into a contracted colloquial form.
Answers: 1. もいい; 2. いけません; 3. いいです; 4. 食べちゃだめ.
What to remember
- Use Vてもいいですか to ask for permission.
- Use Vてもいいです or いいですよ to permit.
- Use Vてはいけません or Vてはだめです to prohibit.
- In casual speech, ては／では can become ちゃ／じゃ.
- Don't confuse “cannot” with Vなくてもいい, which means “don't have to”.
To review how these structures fit into complete sentences, go back to the Basics of Japanese Grammar and practice with different verbs in the て form.
How to ask for permission in Japanese?
Use the verb in て form followed by もいいですか. For example, ここに座ってもいいですか means ‘Can I sit here?’.
How to say that someone can do something because they have permission?
Use Vてもいいです or respond with いいですよ and どうぞ. 写真を撮ってもいいです means that it is allowed to take photos.
What is the difference between てもいい and ことができる?
てもいい deals with permission. ことができる and the potential form mainly indicate ability or possibility, although context sometimes brings the translations closer together.
What does てはいけません mean?
It is a prohibition construction: it informs that a certain action is not permitted. It is formed with the verb in the て form followed by はいけません.
What does ちゃだめ mean?
It's a casual way of prohibition. ちゃ comes from the contraction of ては; thus, 食べてはだめ can become 食べちゃだめ.
Does なくてもいい mean that you can't do something?
No. Vなくてもいい means that it is not necessary to do the action. Vてはいけない indicates that the action is not permitted.
When to use てもいいでしょうか?
Use this form when you want to ask permission more carefully, especially in professional situations or when making a delicate request.
How to respond to a permission request in Japanese?
To allow, use はい、いいですよ or どうぞ. To decline gently, a short excuse or explanation usually sounds more natural than just いいえ.