Posted inN3 Grammar

Explaining Reasons Based on Rules: Understanding 「てはいけないから」 (Because you must not…)

Posted inN3 Grammar
Japanese Grammar Template
Meaning & Usage

✨ Basic Meaning

Because one must not [verb]

🎯 Primary Function

Used to state the reason for an action (or inaction) is that a certain behavior is prohibited or advised against. The ‘because’ clause specifies the prohibition that leads to the consequence in the main clause.

📋 Grammar Structure

[Verb て-form] + はいけない + から

🎭 Usage Contexts

🏢 Formal Situations

Used when explaining rules or policies, though might use slightly more formal endings than just ‘から’.

😊 Informal Situations

Common in daily conversation to explain why someone shouldn’t do something or why you didn’t do something due to a rule/advice.

✍️ Written Language

Found in explanations of rules, signs, or formal reports.

🗣️ Spoken Language

Very common in everyday interactions.

💡 Common Applications

Explaining why an action is forbidden.
Using the prohibition as the direct cause for not doing something or for doing something else.
Example: ここでタバコを吸ってはいけないから、外へ行きましょう。(Because you must not smoke here, let’s go outside.)
Justifying inaction based on a rule.
Explaining why a certain action wasn’t taken because it was prohibited.
Example: 先生に相談してはいけないと言われたから、自分で解決しようと思った。(Because my teacher told me I must not consult with them, I thought I’d try to solve it myself.)
Giving advice based on something that shouldn’t be done.
Using the prohibition as the basis for recommending an alternative action or caution.
Example: 遅くまで勉強してはいけないから、早く寝た方がいいよ。(Because you must not study until late, it’s better to go to bed early.)
📊
Frequency
Moderately frequent, especially when discussing rules, regulations, or necessary behaviors.
🎚️
Difficulty
N3
Example Sentences
ここに車を停めてはいけないから、別の場所を探しましょう。
Because you must not park your car here, let’s look for a different spot.
夜遅く一人で出かけてはいけないから、気をつけてください。
Because you must not go out alone late at night, please be careful.
試験中は携帯電話を使ってはいけないから、電源を切っておいてください。
Because you must not use mobile phones during the exam, please turn off the power.
Notes & Nuances

📌 Important Points

The reason given by 「てはいけないから」 is the prohibition itself.
The phrase indicates that the subsequent action or state is a direct result of the rule or advice that something is forbidden.
Example: ここで走ってはいけないから、歩きましょう。(Because you must not run here, let’s walk.) – The reason for walking is the rule about not running.
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⚠️ Common Mistakes

❌ Using it just to state a prohibition.
✅ Remember it’s “prohibition + reason/cause”. It needs a second clause explaining what happens *because* of the prohibition.
「ここで走ってはいけない。」 (Don’t run here.) is a prohibition. While 「ここで走ってはいけないから、危ないです。」 (Because you must not run here, it’s dangerous.) is grammatically possible, a more common usage for N3 is linking it to another action: 「ここで走ってはいけないから、歩いてください。」 (Because you must not run here, please walk.)
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🏛️ Cultural Context

Politeness Level: Can sound a bit direct, especially when telling someone else what *they* must not do. Often softened with other particles or polite endings in the main clause.
Social Situations: Used when explaining rules in schools, workplaces, public places, or giving parental advice.
Regional Variations: 「てはだめだから」「ちゃいけないから」 etc. might be used informally depending on region/speaker.

🔍 Subtle Differences

「～てはいけないから」 vs 「～から、～てはいけない」
「～てはいけないから」 puts the *reason* (the prohibition) first, leading to a consequence/action. 「～から、～てはいけない」 gives a *reason* first (e.g., it’s dangerous) and then states the prohibition (e.g., so you mustn’t run). The focus is different.
When to use: Use 「てはいけないから」 when the *fact* that something is prohibited is the direct *cause* or *justification* for what follows. Use 「～から、～てはいけない」 when a separate reason (danger, health, etc.) is the basis for the prohibition itself.
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📝 Conjugation Notes

Review て-form conjugation for Ichidan, Godan, and Irregular verbs.

🔊 Pronunciation Tips

「ては」 often becomes 「ちゃ」 informally, leading to 「ちゃいけないから」 or 「じゃいけないから」 (depending on the preceding sound).

🧠 Memory Tips

Think of it as “Because doing [X] is forbidden, [Y happens/should happen]”. The “forbidden” part is the reason for the action/inaction that follows.

Practice Exercises
図書館では騒い（　　）から、静かにしましょう。
いけない
いけないで
てはいけないから
てはいけないで
授業中に寝て（　　）から、集中して聞きましょう。
いけない
はいけない
はいけないから
はいけないために
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