chīfàn qián qǐng xiān xǐshǒu.

Because in Chinese, 前 works like a postposition here: it comes after the event or action.

• 吃饭前 = before eating / before the meal
• Compare:
  • 睡觉前 = before sleeping
  • 上课前 = before class

So instead of saying before eat, Chinese says something closer to eat-meal before.

It can mean either one, and in this sentence both ideas overlap naturally.

• 吃饭 literally means eat a meal
• 吃饭前 can mean:
  • before eating
  • before the meal
  • before you eat

In everyday use, people usually do not separate those meanings very sharply.

请 makes the sentence polite. In this sentence it means please.

So:

• 洗手 = wash your hands
• 请洗手 = please wash your hands

A very common pattern in Mandarin is:

• 请 + verb

Examples:

• 请坐 = please sit
• 请等一下 = please wait a moment

Also, 请 can mean invite in other sentences, but not here.

This is a very common learner question. 前 and 先 are related, but they do different jobs.

• 吃饭前 sets the time frame: before eating
• 先 shows the sequence of actions: first

So the sentence is like:

• Before eating, please first wash your hands.

In natural English, we often do not translate both separately, but in Chinese it sounds very normal to use both.

If you remove 先, the sentence still works:

• 吃饭前请洗手

But 请先洗手 sounds especially natural in reminders and instructions.

Chinese often leaves out the subject when it is obvious.

This sentence is an instruction or polite command, so the subject is understood as:

• you
• or everyone in general

That is very common in Mandarin, especially in:

• signs
• rules
• reminders
• polite instructions

So 吃饭前请先洗手 naturally means:

• Before eating, please wash your hands first
• or Please wash your hands before eating

without needing 你.

Because Chinese usually does not state the possessor for body parts when it is obvious.

So:

• 洗手 naturally means wash your hands
• not just wash hands in some vague sense

Chinese often omits words like your, my, or his with body parts if the meaning is clear from context.

Compare:

• 抬头 = raise your head
• 闭眼 = close your eyes
• 洗手 = wash your hands

You would only add 你的 if you needed special emphasis or contrast.

Chinese usually does not mark plural on nouns unless it really needs to.

So 手 can mean:

• hand
• hands

The context tells you which one is meant.

In 洗手, everyone understands it as wash your hands. Chinese does not need a separate plural ending like English -s.

Yes, you can.

Both are natural:

• 吃饭前请先洗手
• 在吃饭前请先洗手

Adding 在 makes the time phrase a little more explicit, like at/before the time of eating, but it is often unnecessary.

The version without 在 is very common and concise, especially in reminders and signs.

Yes. 吃饭之前 is also very natural.

These are all possible:

• 吃饭前
• 吃饭之前
• 吃饭以前

The differences are small here:

• 前 is short and concise
• 之前 is very common and slightly fuller
• 以前 can also mean before, though in some contexts it may feel a bit broader

For this sentence, 吃饭前 is simple and very natural.

In careful dictionary form, it is:

• 洗手 = xǐ shǒu

Both syllables are third tone, but in normal speech, when one third tone comes before another third tone, the first one usually changes in pronunciation.

So xǐ shǒu is commonly pronounced more like:

• xí shǒu

This is standard third-tone sandhi.

So learners often hear:

• written: xǐshǒu
• spoken: approximately xíshǒu

It sounds natural. It is the kind of sentence you might hear or read in:

• a school
• a home
• a kindergarten
• a restaurant sign
• a public health reminder

It has a polite, instructional tone.

A parent might also say something very similar to a child. In casual speech, people might make it softer or more conversational, but 吃饭前请先洗手。 is absolutely normal Mandarin.

No. Standard Chinese writing normally does not use spaces between words.

So the sentence is usually written as:

• 吃饭前请先洗手。

Learning materials often add spaces to help learners see the word boundaries:

• 吃饭 / 前 / 请 / 先 / 洗手

That is for readability only. In normal Chinese text, the spaces are not used.