What is てもいい?
てもいい is how you ask for permission, grant permission, or deny it in Japanese. "May I sit here?" "Can I borrow this?" "You can't smoke in here." All of these situations use patterns built on the て form.
Our lesson on polite requests and permission covers these patterns alongside てください and other request forms. Here we'll break down the grammar in detail.
Asking Permission: てもいいですか？
Take the て form of the verb, add もいいですか:
| Dictionary | Permission Question |
|---|---|
| 見る | 見てもいいですか？ |
| 使う | 使ってもいいですか？ |
| 座る | 座ってもいいですか？ |
| 食べる | 食べてもいいですか？ |
The literal meaning is something like "even if I do ~, is it good?" which naturally becomes "May I ~?"
Giving Permission: てもいいです
Drop the か and you're giving permission:
- 食べてもいいですよ。
You may eat (it). / It's OK to eat. - 帰ってもいいです。
You may go home.
Denying Permission: てはいけません
This is the "you must not" pattern. Replace もいい with はいけません:
| Dictionary | Prohibition |
|---|---|
| 走る | 走ってはいけません |
| 触る | 触ってはいけません |
| 入る | 入ってはいけません |
てはいけません is firm -- it's a rule or strong prohibition. Think "you must not" rather than a soft "please don't" (that's more ないでください territory). The は in てはいけません is read わ, not は.
This is different from the negative imperative (するな), which is a blunt command. てはいけません states a rule; するな barks an order.
Casual Versions
In everyday conversation, these get shortened:
| Polite | Casual |
|---|---|
| てもいいですか？ | てもいい？ |
| てはいけません | ちゃだめ / じゃだめ |
The casual prohibition works like this: てはだめ contracts to ちゃだめ (after て), and ではだめ contracts to じゃだめ (after で):
- 食べてはだめ → 食べちゃだめ (you can't eat that)
- 飲んではだめ → 飲んじゃだめ (you can't drink that)
Answering Permission Questions
When someone asks てもいいですか, you can respond:
| Response | Meaning |
|---|---|
| はい、いいですよ。 | Yes, go ahead. |
| はい、どうぞ。 | Yes, please do. |
| すみません、ちょっと... | Sorry, that's a bit... (soft refusal) |
| いいえ、いけません。 | No, you may not. (direct) |
The indirect refusal (ちょっと...) is very common. Japanese speakers often soften a "no" rather than saying it outright.
Example Sentences
-
写真を撮ってもいいですか？ (shashin wo totte mo ii desu ka?)
May I take a photo? -
ここに座ってもいい？ (koko ni suwatte mo ii?)
Can I sit here? -
この本を借りてもいいですか？ (kono hon wo karite mo ii desu ka?)
May I borrow this book? -
もう帰ってもいいですよ。 (mou kaette mo ii desu yo.)
You may go home now. -
ここでタバコを吸ってはいけません。 (koko de tabako wo sutte wa ikemasen.)
You must not smoke here. -
授業中にスマホを使っちゃだめ。 (jugyouchuu ni sumaho wo tsukaccha dame.)
You can't use your phone during class. -
窓を開けてもいいですか？ (mado wo akete mo ii desu ka?)
May I open the window? -
ここで泳いではいけません。 (koko de oyoide wa ikemasen.)
You must not swim here.