Learn Hardcore Japanese: kinou ha hoteru no yoyakukin wo haraimasita. - I paid the deposit for the hotel yesterday.

In Japanese, は marks the topic of the sentence, and time expressions often become topics. By saying 昨日は, you’re setting “as for yesterday” as the frame for what happened. Using が here would mark “yesterday” as the subject, which is less natural for time phrases. Omitting the particle is possible in casual speech, but in polite/formal sentences you usually include は.

Why is there no particle directly after ホテル, and instead we have の?

の is the possessive/modifying particle. ホテルの予約金 literally means “the hotel’s reservation deposit.” If you wrote ホテル予約金, it wouldn’t clearly show that the deposit belongs to the hotel reservation—you need の to link “hotel” and “reservation deposit.”

What does 予約金 mean?

予約金 (よやくきん) means “reservation deposit” or “booking fee.” It’s the amount you pay in advance to hold or secure a reservation.

Why is the particle を used after 予約金?

を marks the direct object of the verb. Since 予約金 is what you paid, it’s the object of 払いました (paid), so you say 予約金を払いました.

Why is the verb 払いました in past tense?

Because the action happened in the past—specifically, yesterday. Japanese verbs change form to show tense. 払います is present/future, and 払いました is past.

Why is ホテル written in katakana instead of kanji?

ホテル is a foreign loanword (from the English “hotel”), so it’s written in katakana. Native Japanese words use kanji or hiragana; loanwords use katakana.

How do you pronounce 予約金?

You pronounce it as よ・やく・きん (yo-ya-ku-kin) with the main stress on the first mora: YO-ya-ku-kin.

What’s the difference between 予約金 and 預金?

Although they sound similar, 予約金 means “reservation deposit” (fee you pay to hold a booking), while 預金 (よきん) means “bank deposit” (money you keep in a bank account). They use different kanji and have different meanings.

Could I use 支払いました instead of 払いました?

Yes. 払いました and 支払いました both mean “paid,” but 支払う (しはらう) is slightly more formal or explicit. In this polite sentence, either is acceptable:

昨日はホテルの予約金を払いました。
昨日はホテルの予約金を支払いました。

Is it okay to rearrange the sentence more casually, for example 昨日ホテルの予約金を払った?

Yes. Dropping は and using the plain past form 払った is fine in casual speech:
昨日　ホテルの予約金を払った。
This feels less formal than the original polite version.