hoteru ga heya wo kakuhosita.

が marks the grammatical subject of the sentence: the thing that performs the action.

So in ホテルが部屋を確保した, ホテル is the subject, meaning the hotel is the one that secured or set aside the room.

A learner often compares が and は here:

• ホテルが = emphasizes the hotel as the doer
• ホテルは = would make the hotel the topic, with a slightly different feel

In an isolated sentence like this, が is very natural for introducing who did the action.

を marks the direct object: the thing directly affected by the action.

Here:

• 部屋 = room
• 部屋を = the room is what was secured

So the structure is:

• ホテルが = the hotel did it
• 部屋を = the room was acted on
• 確保した = secured

Yes, grammatically that is what the Japanese sentence says.

Japanese often allows organizations, businesses, or places to act as the subject of a verb, just like English can say:

• The company decided
• The school announced
• The hotel secured a room

So ホテルが means the hotel, as an institution or staff acting for it, secured the room.

Depending on context, the natural English interpretation might be something like:

• The hotel secured a room.
• The hotel arranged a room.
• The hotel set aside a room.

確保した is the past form of 確保する, which means:

• to secure
• to ensure
• to obtain and keep available
• to reserve or set aside, depending on context

The core idea is making sure something is available or protected.

So 部屋を確保した suggests more than just noticing a room; it means the room was successfully obtained, set aside, or made available.

確保した is the plain past form, so it means secured.

Compare:

• 確保する = secure / will secure
• 確保した = secured

So this sentence is talking about a completed action in the past.

If you wanted a polite version, it would be:

• ホテルが部屋を確保しました。

Japanese word order is more flexible than English because particles show each word’s role.

The basic order here is:

• ホテルが部屋を確保した

But you could also say:

• 部屋をホテルが確保した

and it would still be grammatically understandable because:

• が still marks the subject
• を still marks the object

That said, the original order is the most neutral and straightforward.

By itself, 部屋 does not tell you whether it is:

• a room
• the room
• rooms

Japanese usually does not mark articles like a or the, and it often does not mark plural unless necessary.

So the exact English translation depends on context. In many cases, this sentence would naturally be understood as:

• The hotel secured a room

But another context could support:

• The hotel secured the room
• The hotel secured rooms

Because ホテルが部屋を確保した does not mean the hotel room secured... or the hotel’s room... as one noun phrase.

Instead, it is a full sentence with:

• ホテルが = subject
• 部屋を = object

If you used の, the meaning would change:

• ホテルの部屋 = the hotel’s room / a room in the hotel

So compare:

• ホテルが部屋を確保した = The hotel secured a room.
• ホテルの部屋 = a hotel room / the hotel’s room

Yes. ホテル is a loanword written in katakana.

Katakana is often used for foreign-derived words. The pronunciation is roughly hoteru.

A native English speaker should be careful not to pronounce it exactly like English hotel. Japanese syllables are more even:

• ho-te-ru

Yes. 確保する is a very common verb used for many kinds of things that are obtained, guaranteed, or set aside.

Examples:

• 時間を確保する = secure time
• 人材を確保する = secure personnel
• 安全を確保する = ensure safety
• 座席を確保する = secure a seat

So 部屋を確保した fits a broader pattern: something needed was successfully made available.

Yes, it would be grammatically correct, but the nuance changes.

• ホテルが部屋を確保した
  Focuses on who secured the room. It can sound like it was the hotel that secured the room.

• ホテルは部屋を確保した
  Makes the hotel the topic. It can sound more like as for the hotel, it secured a room.

In a simple standalone sentence, が is very natural if you are identifying the subject of the action.