syuuten de oriru mae ni, wasuremono ga nai ka kakuninsimasu

Because Vる + 前に means before doing V.

So:

• 降りる前に = before getting off

With 前に, Japanese normally uses:

• the dictionary form for verbs
• a noun + の for nouns

Examples:

• 寝る前に = before sleeping
• 食べる前に = before eating
• 出発の前に = before departure

So 降りる前に is the standard pattern.

終点 means the final stop / end of the line.

The particle で here marks the place where the action happens. Since 降りる is the action of getting off, 終点で降りる means:

• get off at the final stop

Even though English often uses at, Japanese uses で because it marks the location of the action.

So:

• 終点で降りる = get off at the last stop

In this pattern, 前に is the normal set expression meaning before.

So:

• 降りる前に = before getting off

You should think of 前に as one grammatical chunk here, not as two separate words you can freely change.

忘れ物 means something forgotten, usually an item you accidentally leave behind.

It is made from:

• 忘れる = to forget
• 物 = thing

So 忘れ物 is not the act of forgetting in general. It usually means a physical forgotten item, like:

• a bag
• an umbrella
• a phone

In this sentence, it means something like any belongings left behind.

Here, 忘れ物 is the thing whose existence is being checked.

• ある / ない talk about existence
• the thing that exists or does not exist is often marked by が

So:

• 忘れ物がない = there are no forgotten items / you haven’t left anything behind

That is why が is natural here.

It is not:

• 忘れ物をない — this is incorrect

ないか here means whether there isn’t / whether there are no ...

The か turns the preceding clause into an indirect question:

• 忘れ物がない = there are no forgotten items
• 忘れ物がないか確認します = check whether there are no forgotten items

In more natural English, this becomes:

• check that you haven’t left anything behind

So this is not a direct question being asked out loud. It is an embedded whether clause.

Because 確認する often means to check whether X is true.

Here, what is being checked is not the forgotten item itself, but the condition:

• whether there is any forgotten item

So:

• 忘れ物を確認します would sound more like I check the forgotten item
• 忘れ物がないか確認します means I check whether I have left anything behind

That is the important difference.

Formally, yes: します is non-past polite form.

But in Japanese, non-past can express several things, including:

• habitual actions
• future actions
• instructions or general procedures, depending on context

In a sentence like this, it often sounds like:

• a general instruction
• a routine action
• something you should do

So it can naturally mean something like:

• Before getting off at the final stop, check that you haven’t left anything behind.

Yes. Japanese often leaves the subject unstated when it is obvious from context.

This sentence does not explicitly say:

• you
• I
• passengers

Depending on context, it could mean:

• I check...
• You should check...
• Passengers are asked to check...

In transportation announcements or instructional language, the implied subject is often you.

The sentence has two main parts:

1. 終点で降りる前に
   = before getting off at the final stop

2. 忘れ物がないか確認します
   = check whether you have left anything behind

So the structure is:

• [Before doing X], [do Y].

This is very common in Japanese.

Yes, but the nuance changes a little.

• 終点 = the end of the line; very common in train/bus contexts
• 最終駅 = final station; also possible, a bit more formal or technical
• 最後の駅 = the last station; understandable, but less fixed as transport wording

In announcements and practical travel Japanese, 終点 is very natural.

The comma is there to make the sentence easier to read.

It separates:

• the before... part
• from the main action

So:

• 終点で降りる前に、忘れ物がないか確認します

This kind of comma is very common after a long introductory phrase, but punctuation in Japanese is somewhat flexible. Sometimes you may see similar sentences without a comma.

A natural reading is:

• しゅうてん で おりる まえ に、わすれもの が ない か かくにん します

Word by word:

• 終点 → しゅうてん
• で
• 降りる → おりる
• 前に → まえに
• 忘れ物 → わすれもの
• が
• ない
• か
• 確認します → かくにんします

Yes, literally that is close.

But in natural English, we usually say:

• check that you haven’t left anything behind
• make sure you don’t leave anything behind

So the literal structure is:

• forgotten-item(s) + do not exist + whether

But the natural meaning is simply:

• make sure you have all your belongings