kodomo wo kuruma ni tozikomenaide kudasai.

を marks the direct object of the verb.

In this sentence, 子供を means the child / children is the thing being affected by the action 閉じ込める.

So:

• 子供を = the child(ren) as the object
• 閉じ込めないでください = please do not lock in / shut in

In English, we do not usually mark the object with a special word, but Japanese does.

Here, に marks the place where someone ends up being shut in.

So 車に閉じ込める means to shut someone in a car.

Why not the others?

• 車に = in/into the car as the location of confinement
• 車を would make car the direct object, which does not fit here
• 車で often marks means or location of an action in some cases, but not the destination/place of being enclosed in this expression

With 閉じ込める, the pattern is often:

• person を place に 閉じ込める

For example:

• 猫を部屋に閉じ込めた。 = I shut the cat in the room.

This is a polite negative request: Please do not ...

It breaks down like this:

• 閉じ込める = to shut in / lock in / confine
• 閉じ込めない = do not shut in / not shut in
• 閉じ込めないで = without shutting in / don’t shut in
• 閉じ込めないでください = please do not shut in

So this is a standard way to tell someone politely not to do something.

A very common pattern is:

• verbないでください = please do not verb

Examples:

• 入らないでください。 = Please do not enter.
• 触らないでください。 = Please do not touch.

Because 閉じ込める has a more specific meaning.

• 閉める = to close
• 閉じ込める = to shut/lock someone or something inside a place

So if you just used 閉める, it would mean something like close a door or window, but it would not clearly express the idea of trapping someone inside.

閉じ込める combines the idea of closing with putting/keeping someone inside.

It can mean either a child or children, depending on context.

Japanese nouns usually do not change form for singular vs. plural the way English nouns do.

So 子供を could mean:

• a child
• children

If the speaker wants to make plurality clearer, context usually does the job. Sometimes Japanese may use words like 子供たち, but that is not always necessary.

No, that is usually just for learners.

Normal Japanese writing would usually be:

子供を車に閉じ込めないでください。

Japanese normally does not use spaces between words the way English does. Textbooks and beginner materials often add spaces to make the grammar easier to see.

Yes, it is polite.

The ください part makes it a polite request.

So 閉じ込めないでください is a polite way to say:

• Please do not lock/shut (someone) in

It is not as direct or rough as simply saying:

• 閉じ込めるな = Don’t lock someone in.

So the sentence is appropriate for warnings, signs, instructions, or polite spoken requests.

It usually suggests that someone is being kept inside a place and cannot easily get out. It often has a strong nuance of confinement, being trapped, or being shut in.

So this sentence does not just mean don’t put a child in a car. It specifically means something closer to:

• don’t leave a child shut inside a car
• don’t lock a child in a car
• don’t confine a child in a car

The exact English translation can vary, but the Japanese verb strongly suggests being enclosed or trapped.

Yes. Both 子供 and 子ども are common.

Some people prefer 子ども because the mixed writing style is often seen as softer or more standard in certain educational contexts. Others use 子供 normally in everyday writing.

So for learners, it is useful to recognize both:

• 子供
• 子ども

They mean the same thing here.

Japanese often puts information before the verb, and the verb comes at the end.

A basic way to see this sentence is:

• 子供を = the child(ren)
• 車に = in the car
• 閉じ込めないでください = please do not shut/lock in

So Japanese builds the sentence piece by piece, then finishes with the action.

A very common pattern is:

• object を place に verb

In English, we often say:

• Please do not lock children in the car.

In Japanese, the verb comes last:

• 子供を車に閉じ込めないでください。

It can be translated that way in some real-world situations, especially on warning signs, but grammatically it is more specific than just leave.

閉じ込める implies shutting/locking someone inside. So:

• Don’t leave a child in the car is a natural English warning
• but the Japanese literally has the stronger idea of don’t shut/lock a child inside the car

So the natural English translation may be broader, but the Japanese verb itself is more vivid and specific.