souko ni hako wo oita.

It is read:

そうこ に はこ を おいた。

Word by word:

• 倉庫 = そうこ = warehouse
• 箱 = はこ = box
• を is pronounced o
• 置いた = おいた = placed / put

Here is the basic breakdown:

• 倉庫 = warehouse
• に = marks the location where something ends up
• 箱 = box
• を = marks the direct object
• 置いた = put down / placed

So structurally, it is:

warehouse + in/at + box + object marker + placed

Because に marks the place where the box is placed.

With a verb like 置く, the location marked by に is the destination or resting place of the object. In this sentence, the box ends up in the warehouse, so 倉庫に is natural.

A useful idea is:

• に = where something goes / ends up
• で = where an action happens

Since 置く is about putting something somewhere, に is the usual choice.

Because 箱 is the thing being acted on.

The verb 置く means to place / to put, and the box is what is being placed, so it takes を, the direct object marker.

So:

• 箱を置いた = placed the box

If you are thinking in English grammar terms, 箱 is the object of the verb.

置いた is the plain past form of 置く.

• dictionary form: 置く = to place / to put
• plain past: 置いた = placed / put

This form is often used in:

• casual speech
• written narration
• subordinate clauses

The polite past version would be:

• 置きました

So 倉庫に箱を置きました is the polite version of the same sentence.

The subject is omitted.

This is very common in Japanese. If the speaker, listener, or context already makes the subject clear, Japanese often leaves it out.

So this sentence could mean:

• I placed the box in the warehouse
• He placed the box in the warehouse
• She placed the box in the warehouse
• They placed the box in the warehouse

The sentence itself does not specify who did it.

Not completely.

Japanese word order is more flexible than English because particles show each word’s role. The most important rule is that the verb usually comes at the end.

So these are both possible:

• 倉庫に箱を置いた
• 箱を倉庫に置いた

They mean essentially the same thing. The difference is mostly about emphasis or flow.

The original order is very natural and straightforward.

Japanese particles do not match English prepositions one-to-one.

Here, に does not literally mean only to, in, or at. It marks the location connected to the result of the action. In English, that may be translated in different ways depending on context.

So:

• 倉庫に置いた can be translated as put it in the warehouse
• in another context, に might sound more like at or to

It is better to think of に as a grammatical marker, not as a single fixed English word.

The particle を is traditionally written with the kana を, but in modern Japanese it is pronounced o.

So in this sentence:

• written: 箱を
• spoken: はこ o

This is normal and something all learners need to get used to. As a particle, を is almost always pronounced o.

Japanese does not have articles like a, an, and the.

So 倉庫 could mean:

• a warehouse
• the warehouse

And 箱 could mean:

• a box
• the box

The exact meaning depends on context.

That is why Japanese sentences often leave this kind of detail unstated unless it really matters.

Sometimes, but the nuance changes.

• 置いた = placed / put down somewhere
• 入れた = put into / inserted

So:

• 倉庫に箱を置いた focuses on placing the box in the warehouse
• 倉庫に箱を入れた would suggest putting the box into the warehouse, with more emphasis on moving it inside

In many situations both could make sense, but 置いた sounds more like the final placement, while 入れた emphasizes putting something into a space.

Yes, 置く is a very common verb.

It is used when you place something somewhere, especially as a completed placement.

Examples:

• 机の上に本を置く = put a book on the desk
• 床にかばんを置く = put a bag on the floor
• 倉庫に箱を置く = put a box in the warehouse

It often implies that the object is left resting there after being placed.