nimotu ha souko ni aru.

は marks 荷物 as the topic of the sentence: as for the luggage.

So 荷物は倉庫にある is literally something like:

As for the luggage, it is in the warehouse.

In many cases, this feels very natural in Japanese when you are talking about something already known in the conversation.

If you used が instead, 荷物が倉庫にある, it would sound more like you are specifically identifying or emphasizing that the luggage is what is in the warehouse.

A simple way to remember it:

• は = topic, background, what you're talking about
• が = subject, often more focused or identifying

Here, に marks the location of existence.

With verbs like ある and いる, に shows where something exists/is located.

So:

• 倉庫にある = to be in the warehouse

This is different from some other uses of に, such as time, destination, or indirect object. In this sentence, it specifically marks the place where the luggage is.

Japanese uses different verbs for existence depending on whether something is animate or inanimate.

• いる is used for people and animals
• ある is used for things and objects

Since 荷物 means luggage/baggage, it is an object, so ある is correct.

Examples:

• 人は部屋にいる。 = The person is in the room.
• 荷物は倉庫にある。 = The luggage is in the warehouse.

Not in this sentence.

に is used because the sentence is about where something exists.

• 倉庫にある = it exists/is located in the warehouse

で usually marks the place where an action happens.

For example:

• 倉庫で働く = to work in the warehouse
• 倉庫で荷物を探す = to look for luggage in the warehouse

Since ある is not an action like working or searching, but a state of existence, に is the natural choice.

The sentence follows a very common Japanese pattern:

Topic + place + verb

So:

• 荷物は = as for the luggage
• 倉庫に = in the warehouse
• ある = exists / is

Japanese verbs usually come at the end of the sentence. That is one of the biggest differences from English.

English:

• The luggage is in the warehouse.

Japanese:

• Luggage + warehouse + in + is

It can mean either, depending on context.

Japanese nouns usually do not show singular vs. plural in the way English nouns do. So 荷物 could mean:

• a piece of luggage
• luggage
• baggage
• bags

The listener understands the exact meaning from the situation.

That means 荷物は倉庫にある could mean:

• The luggage is in the warehouse.
• The bags are in the warehouse.
• A package is in the warehouse.

Context decides which English translation fits best.

The words are read like this:

• 荷物 → にもつ
• 倉庫 → そうこ
• に → に
• ある → ある

So the full sentence is:

にもつ は そうこ に ある。

In normal speech, は is written with the hiragana は but pronounced わ as a particle.

So you would say it like:

にもつ わ そうこ に ある。

Yes, ある is the plain form.

The polite form is あります.

So the polite version is:

荷物は倉庫にあります。

This is what you would likely use in customer service, at work, or when speaking politely.

Compare:

• 荷物は倉庫にある。 = plain
• 荷物は倉庫にあります。 = polite

Japanese does not have articles like English a, an, or the.

So 荷物 by itself does not tell you whether it means:

• a piece of luggage
• the luggage
• some luggage

The context tells you.

This is very common in Japanese. Learners often want every noun to match an English article, but Japanese simply does not work that way.

Yes, exactly.

Because of は, the sentence often has that as for... feeling, even if English translations do not always show it directly.

For example, if someone asks:

• 荷物はどこ？ = Where is the luggage?

You could answer:

• 荷物は倉庫にある。 = The luggage is in the warehouse.

But if several things are being discussed, は can make it feel like:

• As for the luggage, it’s in the warehouse.

So は often adds a contrastive or topical nuance that English may leave unspoken.

Yes. A few natural variations are possible depending on nuance.

For example:

• 荷物が倉庫にある。
  This puts more focus on the luggage itself.

• 荷物は倉庫の中にある。
  This explicitly says inside the warehouse.

• 倉庫に荷物がある。
  This can sound more like There is luggage in the warehouse.

These all relate to the same basic idea, but the emphasis changes a little depending on the particles and word order.

Both, in a way.

With ある, Japanese often expresses location through the idea of existence.

So instead of directly saying is located, Japanese often says something closer to:

The luggage exists in the warehouse.

Of course, in natural English, you would usually translate that as:

The luggage is in the warehouse.

This is an important pattern in Japanese:

• X は / が Y にある = X is in Y
• literally: X exists in Y

Understanding that pattern makes many Japanese sentences much easier to follow.