syuumatu ni heya wo kirei ni simasu.

I clean my room on the weekend.

Breakdown of syuumatu ni heya wo kirei ni simasu.

• を: direct object particle
• に: time particle
• 週末しゅうまつ: weekend
• 部屋へや: room
• きれい に する: to clean

Questions & Answers about syuumatu ni heya wo kirei ni simasu.

Why is there a に after 週末?

に marks a point in time when something happens.

• 週末に = on the weekend / at the weekend
• It’s like saying “at/on” in English time phrases.

You normally use に after specific times, days, or dates:

• ３時に – at 3 o’clock
• 日曜日に – on Sunday
• ４月に – in April

So 週末に部屋をきれいにします = “I will clean my room on the weekend.”

If you say 週末は, it’s more like “as for weekends / on weekends (in general) …” and often sounds more habitual:

• 週末は部屋をきれいにします。
  → “On weekends, I (usually) clean my room.”

Why is きれい followed by に? What does きれいに mean?

きれい is a na-adjective (きれいな), not a verb.
To turn a na-adjective into an adverb-like form, you add に:

• きれい → きれいに (cleanly / in a clean state)

Then Japanese uses the verb する “to do/make”:

• きれいにする = “to make (something) clean / to tidy (something) up”

So in the sentence:

• 部屋をきれいにします
  literally: “(I) will make the room clean.”

Grammatically:
部屋（object）+ を + きれいに（adverb-like) + します（do/make）

Is きれい a verb here?

No. きれい is an adjective meaning “clean / neat / pretty.”

The verb in the sentence is します (from する).
きれいにする is a set pattern:

• [na-adjective] + に + する → “to make [something] [adjective]”
  • きれいにする – make (something) clean
  • 静かにする – make (something) quiet / be quiet
  • 便利にする – make (something) convenient

So you should think of きれいにする as one unit: “to clean / to tidy up.”

What does します mean here? Is it just “do”?

Literally, する means “to do,” but in patterns like X にする it often means “to make X (be in that state).”

So:

• きれいにする = “make (it) clean”
• きれいにします = polite form: “I will make (it) clean” → “I will clean (it).”

In this sentence, します is part of the fixed expression きれいにします, not a separate “do something” like in English “do homework.”

Why is 部屋 followed by を? In English “clean” doesn’t always feel like it takes an object in the same way.

In Japanese, 部屋 is clearly the direct object of the action:

• 部屋をきれいにします。
  literally: “(I) will make the room clean.”

を marks what is being affected by the verb. English often says “clean the room” (room = object of “clean”); Japanese says “make the room clean,” which also treats “room” as the object.

So:
部屋 (room) + を (object marker) = “the room (as the thing you’ll make clean)”

How does 部屋をきれいにします differ from 部屋を掃除します?

Both can be translated as “I will clean my room,” but there is a nuance:

• 部屋を掃除します

  • Uses the noun 掃除 (そうじ) “cleaning” with します “to do”
  • Focuses on the act of cleaning (vacuuming, dusting, etc.)

• 部屋をきれいにします

  • Uses the adjective きれい “clean / neat”
  • Focuses on the resulting state: making the room clean/neat/tidy
  • Can include tidying up, putting things away, organizing, etc.

In many everyday contexts they overlap, and both are fine.
If you specifically mean “do cleaning work,” 掃除します is more direct.
If you mean “get my room into a nice, tidy state,” きれいにします feels very natural.

Why is the subject “I” not written? Where is “I” in this sentence?

Japanese often omits the subject if it’s obvious from context.

In this sentence:

• 週末に部屋をきれいにします。

There is no explicit word for “I,” “you,” “we,” etc., but in a normal conversation about your own plans, the listener will naturally understand it as:

• “I will clean my room on the weekend.”

If you wanted to say it explicitly, you could:

• 私は週末に部屋をきれいにします。
  (私 = I)

But adding 私は is usually unnecessary unless you need to emphasize or clarify the subject (e.g., contrast: “I will clean the room,” not someone else).

Can I change the word order, like 部屋を週末にきれいにします?

Yes, that’s grammatically possible. Japanese word order is relatively flexible as long as particles stay attached to the right words.

• 週末に 部屋を きれいにします。 (original)
  → Neutral, natural: “On the weekend, I will clean my room.”

• 部屋を 週末に きれいにします。
  → Also correct, but slightly less neutral; it puts a bit of focus on “the room” first, then mentions “on the weekend.”

The most common, natural order when giving basic information is:

1. Time expression (週末に)
2. Object (部屋を)
3. Verb (きれいにします)

Why is the verb form します (non-past)? How does this express “will clean” (future)?

Japanese doesn’t have a separate future tense like English. The basic non-past form (する / します) covers both:

• present / habitual
• future

Which meaning it has depends on context and time expressions.

In this sentence:

• 週末に (on the weekend) clearly refers to a future time.
• So きれいにします is naturally understood as “will clean (in the future).”

Similarly:

• 毎日部屋をきれいにします。
  → “I clean my room every day.” (habit)
• あとで部屋をきれいにします。
  → “I’ll clean my room later.” (future)

What’s the difference between 週末に and 週末は in this kind of sentence?

Both can appear with this sentence, but the nuance changes:

1. 週末に部屋をきれいにします。

   • Focus: a specific weekend (often the upcoming one)
   • “I will clean my room on the weekend (this weekend/that weekend).”

2. 週末は部屋をきれいにします。

   • は marks the topic; it often suggests a habit or contrast.
   • “On weekends, I (generally) clean my room.”
   • Could also mean: “As for weekends, I (make it a point to) clean my room.”

So use:

• に for “on (that) weekend” as a time point.
• は when you’re talking about weekends as a general topic or routine.

Are the two に in the sentence the same particle and do they do the same job?

They are the same particle に, but used with different functions:

1. 週末に – time marker

   • “on/at (the time of) the weekend”

2. きれいに – adverb-like / result-state marker with a na-adjective

   • “clean(ly) / in a clean state”

So:

• First に: tells you when the action happens.
• Second に: tells you in what state the object will be made (clean).

Despite being the same particle form, their roles in the sentence are different.