JLPT N4 Masterclass: Expressing Prohibition with 〜てはいけません

Welcome to your definitive guide to mastering 〜てはいけません (te wa ikemasen).

Imagine walking into a quiet Japanese library, a sacred shrine, or a train carriage. You will inevitably encounter rules. In Japanese, when you want to state a flat prohibition—telling someone "you must not" or "you are not allowed to" do something—this is your go-to grammatical structure.

---

1. The Grammar Blueprint

To forbid an action, we combine the Te-form of a verb with はいけません.

$$\text{Verb [Te-form]} + \text{はいけません}$$

Conjugation Quick-Reference:

• Group 1 (U-Verbs): 書く (kaku) $\rightarrow$ 書いて (kaite) $\rightarrow$ 書いてはいけません (Must not write)書
• Group 2 (Ru-Verbs): 食べる (taberu) $\rightarrow$ 食べて (tabete) $\rightarrow$ 食べてはいけません (Must not eat)食
• Group 3 (Irregular): する (suru) $\rightarrow$ して (shite) $\rightarrow$ してはいけません (Must not do)

---

2. Deep Dive: Nuance & Social Context

Why do we use いけません? It originates from the potential verb 行ける (ikeru - to be able to go/be acceptable). Literally, the grammar translates to: "If you do [X], it cannot go forward/it will not work."行

Who uses it, and when?

• Authority Figures: Teachers to students, parents to children, or police officers to citizens.
• Public Signs & Rules: Written instructions on placards or public announcements.
• Polite but Firm: It is grammatically polite (ending in masen), but because it is a direct command, using it with a boss or a social superior can sound rude. To be softer, Japanese speakers prefer: 〜てはだめです (casual) or 〜ないでください (please don't).

---

4. Pro-Tip: The Casual Shortcut (N4 Listening Prep)

In casual, spoken Japanese, 〜ては (te wa) and 〜では (de wa) contract into shorter, punchier sounds. You will hear these constantly in anime, dramas, and daily conversations:

$$\text{〜ては} \rightarrow \text{〜ちゃ} \quad | \quad \text{〜では} \rightarrow \text{〜じゃ}$$

• Polite: 食べてはいけません (You must not eat)食
• Casual: 食べちゃだめ (Tabecha dame)食
• Polite: 飲んではいけません (You must not drink)飲
• Casual: 飲んじゃだめ (Nonja dame)飲

---

5. Quick Challenge!

Test your knowledge. Translate the following sentence into Japanese using 〜てはいけません:

"You must not enter this room."
(Vocabulary Hint: Room = 部屋 heya, To enter = 入る hairu [Group 1])部屋入

<details> <summary><b>Click here to reveal the answer!</b></summary>

Answer:
この部屋に入ってはいけません。
(Kono heya ni haitte wa ikemasen.)部屋入

</details>

3. Real-World Examples

Let’s look at how this grammar functions in everyday N4 contexts.

Example 1: Public Rules

• Japanese: ここで写真を撮ってはいけません。写真撮
• Romaji: Koko de shashin o totte wa ikemasen.
• English: You must not take photos here.
• Breakdown: 撮る (toru - to take a photo) becomes 撮って (totte).撮

Example 2: Classroom Rules

• Japanese: テスト中に辞書を使ってはいけません。中辞書使
• Romaji: Tesuto-chū ni jisho o tsukatte wa ikemasen.
• English: You must not use a dictionary during the exam.
• Breakdown: 使う (utsau - to use) becomes 使って (tsukatte).使

Example 3: Sound Advice / Laws

• Japanese: お酒を飲んで運転してはいけません。酒飲運転
• Romaji: Osake o nonde unten shite wa ikemasen.
• English: You must not drink alcohol and drive.
• Breakdown: 運転する (unten suru - to drive) becomes 運転して (unten shite).運転

---