Learn Hardcore Japanese: yoyakuseki ni nimotu wo oite ha ikemasen. - You must not put luggage on the reserved seat.

In Japanese, に marks the destination or target location of a placement verb like 置く (“to put”). You’re putting your luggage onto the reserved seat, so the seat is the target and takes に. By contrast, で marks the place where an action occurs. If you said 予約席で荷物を置く, it would literally mean “to perform the action of putting luggage at the reserved seat” rather than “to place luggage onto it,” and sounds unnatural in this context.

Why is there a は after 置いて in 置いては?

The は attaches to the て-form of a verb to form the pattern ～ては. When combined with いけません, ～ては turns the verb into a prohibited act. Think of 置いてはいけません as one unit meaning “you must not put (luggage there).” The は here highlights the “act of putting.”

What does ～てはいけません mean and how is it used?

～てはいけません is a set phrase meaning “must not do ~,” “may not do ~,” or “you’re not allowed to ~.” It expresses prohibition based on rules or official regulations. You’ll see it on signs: e.g. ここに駐車してはいけません (“Parking here is not allowed”).

What’s the difference between ～てはいけません, ～てはいけない, and ～てはなりません?

• ～てはいけない is the plain or informal form (“you can’t ~”).
• ～てはいけません is the polite form, common in public notices and formal speech.
• ～てはなりません is even more formal and is often used in written rules, legal texts, or very polite announcements. All three express prohibition.

Can we use ダメ instead of いけません, like 置いてはダメ?

Yes. ～てはダメ (or ～てはダメです) is a casual or slightly softer way to prohibit something. On a sign you might see 荷物を置いてはダメです. In very casual speech people even say 置いちゃダメ (see next question).

Why is 荷物 followed by を in 荷物を置いて?

荷物 is the direct object of the verb 置く (“to put”). In Japanese, you mark a direct object with を. So 荷物を置く means “to put luggage.”

Why is 予約席 used instead of 予約の席?

予約席 is a compound noun meaning “reserved seat,” commonly used in signs and labels. 予約の席 (“seat of reservation”) is also grammatically correct but slightly longer. Japanese often forms concise compounds for everyday terms.

Where is the subject in this sentence? Who is forbidden from doing this?

Japanese often omits the subject when it’s clear from context. On a public sign like this, the implicit subject is “you” (i.e., everyone). So it means “You (anyone) must not put luggage on reserved seats.”

Could we rephrase this sentence as 荷物を置かないでください? What’s the nuance difference?

Yes, you can say 荷物を置かないでください (“Please don’t put your luggage [there]”). That’s a polite request. ～てはいけません expresses a firm rule or prohibition, while ～ないでください is more of a courteous plea.

Can 置いては be contracted to 置いちゃ (as in 置いちゃいけない)?

Absolutely. In casual speech, ては often contracts to ちゃ, so 置いてはいけない → 置いちゃいけない or even 置いちゃダメ. However, on formal signs you would use the full 置いてはいけません.