Learn Hardcore Japanese: kaze no yobou no tame ni, mainiti tearai wo simasu. - I wash my hands every day to prevent colds.

風邪の予防のために、毎日手洗いをします。
- Literally: For the sake of cold prevention, I do hand-washing every day.
- Uses 予防 as a noun: “prevention.”
風邪を予防するために、毎日手洗いをします。
- Literally: In order to prevent colds, I wash my hands every day.
- Uses 予防する as a verb: “to prevent.”

Nuance:

Noun style (風邪の予防のために)
Sounds a bit more formal / textbook / medical. It feels like talking about the general concept or policy of prevention.
Verb style (風邪を予防するために)
Feels a bit more direct and action-focused: “in order to prevent colds (by this action).”

In everyday speech, you will hear both. Textbooks, health posters, and announcements often like the noun style:
風邪の予防のために、うがい・手洗いをしましょう。

What exactly does ために mean here? Is it “for”, “because”, or “in order to”?

ために has two main uses:

Purpose / goal:
- N のために = for / for the sake of N
- V-dictionary-form ために = in order to V
Examples:
- 家族のために、働いています。
  → I work for my family.
- 日本語を勉強するために、日本に行きました。
  → I went to Japan in order to study Japanese.
Reason / cause (often more formal):
- 事故のために、電車が止まりました。
  → The trains stopped because of an accident.

In 風邪の予防のために, it’s clearly the purpose meaning:

For the sake of preventing colds / In order to prevent colds

Why do we need に after ため? Could we say 風邪の予防のため、毎日手洗いをします。 without に?

The basic pattern is:

N のために
V-dictionary-form ために

So strictly speaking, に is part of the normal grammar for “for / in order to”.

However:

In written or slightly formal Japanese, people sometimes drop the に when the phrase comes right before a comma:
- 風邪の予防のため、毎日手洗いをします。 ✅
- 風邪を予防するため、毎日手を洗います。 ✅

Both sound fine. With に, it’s a bit more textbook-like and explicit; without に, it’s slightly more compact and formal-sounding. For learners, it’s safe to remember:

Pattern = 〜ために
Dropping に is optional style, not a different grammar rule.

Is 手洗いをします different from 手を洗います?

Yes, there’s a subtle difference:

手を洗います。
- Literally: wash (my) hands.
- Normal verb phrase. Sounds like a specific action: “I wash my hands.”
手洗いをします。
- 手洗い (てあらい) is a noun meaning “hand-washing” (the act, as an activity/habit).
- Literally: do hand-washing.
- Feels like talking about the practice / habit of hand-washing, not just one instance.

In context:

For a one-off action:
- ちょっと手を洗ってきます。
  → I’ll go wash my hands.
For a habit or instruction (as in posters or health advice):
- 風邪の予防のために、うがい・手洗いをしましょう。
  → For preventing colds, let’s do gargling and hand-washing.

In everyday conversation, 手を洗います is more common, but 手洗いをします is perfectly natural, especially in written or instructional contexts.

Why is the particle を used with 手洗い? I thought する verbs sometimes just attach without を.

Good point. With する-verbs, there are two patterns:

N をする
- 勉強をする (to do study)
- 運動をする (to do exercise)
- 準備をする (to do preparation)
N する
- 勉強する
- 運動する
- 準備する

In many cases, both are possible, and N をする is slightly more explicit that N is an object.

For 手洗い:

手洗いをする ✅ (very common)
手洗いする ✅ (also possible, a bit more casual/short)

Your sentence uses the N をする pattern:
手洗い (noun) + を (object marker) + します (polite する).

So を is normal here; it’s the same structure as 勉強をします, 運動をします, etc.

Could I say 毎日、手を洗います instead? Is that more natural?

Yes, that’s perfectly natural and very common:

風邪を予防するために、毎日手を洗います。
→ In order to prevent colds, I wash my hands every day.

Comparing:

毎日手洗いをします。
- Slightly more instructional / slogan-like (emphasizes the practice of hand-washing).
毎日手を洗います。
- Very straightforward and everyday: “I wash my hands every day.”

Both are correct; which one you choose is mostly style and tone.

Why is 毎日 at the beginning? Can I move it, like 手洗いを毎日します?

Typical Japanese word order is:

[Time] [Object] [Verb]

So:

毎日手洗いをします。
毎日手を洗います。

are the most natural.

You can move 毎日, but some positions sound odd:

手洗いを毎日します。
- Understandable, but sounds unnatural or strongly emphasizes 毎日 in a marked way.
- Native speakers rarely put 毎日 between a noun and its particle like that.

More natural variations:

手洗いは毎日します。
→ As for hand-washing, I do it every day. (emphasizing hand-washing as a topic)
毎日、手洗いをしています。
→ I’m (habitually) doing hand-washing every day.

For time words like 毎日, 今日, 明日, putting them at the start of the sentence without a particle is very standard.

Where is the subject “I” in this sentence? How do we know it means “I wash my hands”?

Japanese often drops the subject if it’s obvious from context. There is no explicit 私 (I) in:

風邪の予防のために、毎日手洗いをします。

But in a neutral context (talking about your own habits), the listener will naturally understand it as:

(私は) 風邪の予防のために、毎日手洗いをします。
(I) wash my hands every day to prevent colds.

Depending on context, it could also mean:

We wash our hands every day
You should wash your hands every day (as advice)
People in general wash their hands every day

Japanese heavily relies on context, so pronouns like 私, あなた, 彼 are omitted unless they’re really needed to avoid confusion or to emphasize.

Why does the sentence use します and not する?

する and します are the plain and polite forms of the same verb:

する = plain (dictionary) form
します = polite 〜ます form

Your sentence is in polite style:

風邪の予防のために、毎日手洗いをします。 ✅ (polite)

The plain-style equivalent would be:

風邪の予防のために、毎日手洗いをする。 ✅ (plain)

Which one you choose depends on who you’re talking to:

To friends / diary / casual writing → する
To teachers, strangers, at work, or in public instructions → します

Since this sounds like general advice or a polite statement, します is the expected choice.

What exactly does 予防 mean? How is it different from 防ぐ?

予防 (よぼう) is a noun (and also part of 予防する, a verb) meaning “prevention”, especially in a medical / health / safety context.
- 予防接種 (よぼうせっしゅ) = vaccination (literally “prevention injection”)
- 火災予防 = fire prevention
防ぐ (ふせぐ) is a verb meaning “to prevent / to defend against / to block” in a more general sense.
- 事故を防ぐ = prevent accidents
- 攻撃を防ぐ = defend against an attack

In your sentence:

風邪の予防 = prevention of colds (concept, strategy)
If you use the verb: 風邪を予防する = to prevent colds

You wouldn’t usually say 風邪を防ぐ; it’s not wrong grammatically, but it’s not the natural collocation. For colds, Japanese almost always uses 予防する or the phrase 風邪をひかないように.

What’s the difference between 風邪の予防のために and 風邪をひかないように?

Both can be translated as “to avoid catching a cold / to prevent colds”, but they use different grammar and nuance:

風邪の予防のために、毎日手洗いをします。
- Uses 予防 (prevention) + ために (for the sake of).
- Sounds more formal, technical, or policy-like.
- Often used in written materials, posters, announcements.
風邪をひかないように、毎日手を洗います。
- Uses 風邪をひく (“to catch a cold”) + ないように (“so that [I] don’t …”).
- Literally: So that I don’t catch a cold, I wash my hands every day.
- Feels more conversational and direct, focusing on the result (not catching a cold).

Pattern-wise:

V-dictionary ために = in order to do V (purpose)
V-ないように = so that [something] doesn’t happen / to avoid V

Both are common; choice depends on how formal or natural/conversational you want to sound.

Is the comma after に necessary in …ために、毎日…?

The comma 、 is not grammatically required, but it is normal and recommended for readability.

風邪の予防のために毎日手洗いをします。 ✅
風邪の予防のために、毎日手洗いをします。 ✅

Both are correct. Japanese punctuation is more flexible than English; commas are largely about where the speaker would naturally pause. After a fairly long modifier like 風邪の予防のために, inserting a comma makes the sentence easier to read and process.