qǐng bǎochí ānjìng.

Yes—请 here works very much like please.

In 请保持安静, 请 makes the sentence polite and appropriate for signs, announcements, instructions, and formal requests.

A few useful notes:

• 请 + verb phrase = please + verb phrase
• 请保持安静 = Please remain quiet / Please keep quiet
• It is common in public notices and announcements.

However, 请 is not always a perfect one-to-one match for English please. In other contexts, 请 can also mean to invite or to treat someone to something, but in this sentence it clearly means please.

Mandarin often leaves out the subject when it is obvious from context.

In a sentence like 请保持安静, the listener or reader is understood automatically. It is basically directed at:

• you
• everyone here
• all visitors / passengers / audience members, depending on context

So even though there is no written subject, the meaning is still clear.

This is very common in commands and notices:

• 请进。 = Please come in.
• 请坐。 = Please sit down.
• 请勿吸烟。 = Please do not smoke. / No smoking.

Chinese often sounds more natural without an explicit subject in these cases.

Because 保持 means to maintain / to keep / to remain in a state, and 安静 describes the state of being quiet.

So the structure is:

• 保持 = maintain, keep
• 安静 = quiet

Together:

• 保持安静 = keep quiet / remain quiet

If you say just 安静, that can also be used as a command, but it feels shorter and more direct—sometimes even sharper, depending on tone and context.

Compare:

• 请保持安静。 = Please remain quiet.
  
  • more formal
  • common on signs and announcements
• 请安静。 = Please be quiet.
  
  • shorter
  • still fine
• 安静！ = Quiet!
  
  • much more direct

So 保持安静 is a very natural choice when you want a polite, public, formal instruction.

安静 is usually an adjective meaning quiet or peaceful.

In 请保持安静, it is still basically adjectival, but it functions as the state that is being maintained.

You can think of 保持 + state/condition as a common pattern in Chinese:

• 保持安静 = remain quiet
• 保持冷静 = remain calm
• 保持健康 = stay healthy
• 保持清洁 = keep clean

So although English might use a different structure, Chinese naturally allows 保持 to be followed by an adjective-like state.

Yes, it is fairly formal and very common in public or institutional settings.

You might see or hear it in places like:

• libraries
• hospitals
• classrooms
• museums
• theaters
• trains or buses
• exam rooms
• public announcements

It sounds especially natural on signs and over loudspeakers.

If you were speaking casually to a friend, you would probably use something else, such as:

• 小声一点。 = A little more quietly.
• 安静一点。 = Be a little quieter.
• 别说话。 = Don’t talk.

So 请保持安静 is polite, neutral, and somewhat official.

The pinyin is:

• 请 — qǐng
• 保持 — bǎochí
• 安静 — ānjìng

Tones:

• 请 = 3rd tone
• 保 = 3rd tone
• 持 = 2nd tone
• 安 = 1st tone
• 静 = 4th tone

So the full tone pattern is:

3rd + 3rd + 2nd + 1st + 4th

A few pronunciation tips:

• qǐng: the q is a soft, unaspirated sound made with the tongue close to the front of the mouth, somewhat like ch said with a smile.
• -ng at the end of qǐng should be pronounced clearly.
• bǎo rhymes roughly with ow in cow, but with a 3rd tone.
• ānjìng: make sure 静 has a strong falling 4th tone.

In connected speech, Mandarin tones can sound a bit smoother than the textbook forms, but learners should start by saying each tone clearly.

There is no major tone sandhi here that changes the written tones in the way learners often worry about.

The tones remain:

• 请 qǐng — 3rd tone
• 保 bǎo — 3rd tone
• 持 chí — 2nd tone
• 安 ān — 1st tone
• 静 jìng — 4th tone

The main thing to know is that in real speech, a 3rd tone is often not pronounced as a full dip-and-rise unless it is emphasized or said in isolation. So:

• 请 and 保 may sound more like low tones in normal connected speech.

But there is no special change like 3rd tone + 3rd tone becoming 2nd + 3rd across 请 保, because those words are often separated slightly in phrasing, and in any case learners can safely pronounce the dictionary tones first.

Yes, 请安静一点 is possible, but it has a slightly different feel.

Compare:

• 请保持安静。
  = Please remain quiet.

  • formal
  • common on signs and public announcements
  • sounds fixed and official

• 请安静一点。
  = Please be a little quieter.

  • more conversational
  • often said directly to people
  • slightly softer in interpersonal situations

So if you are talking to a person or small group, 请安静一点 can sound more natural.
If you are writing a public notice, 请保持安静 is usually better.

Because the sentence is about staying in a quiet state, not becoming quiet or simply being quiet.

• 保持 = keep / maintain / remain
• 变得 = become
• 是 = be

So:

• 请保持安静。 = Please remain quiet / keep quiet.

If you used 变得, it would mean something more like become quiet, which is not the normal wording for a public instruction.

If you used 是, it would not sound natural here. Chinese does not usually say something like 请是安静.

So 保持 is the correct and natural verb for this meaning.

Yes, it is an imperative sentence—a polite command or request.

Its force is moderate:

• stronger than a suggestion
• softer than a blunt order
• very suitable for formal public language

Because it includes 请, it sounds polite.
Because it is short and direct, it still clearly tells people what to do.

So the overall tone is:

• polite
• firm
• formal
• neutral

It does not sound emotional or angry unless the speaker’s tone of voice makes it sound that way.

Yes. Both are good translations.

A few natural English equivalents are:

• Please keep quiet.
• Please remain quiet.
• Please be quiet.
• Please keep silent. (a bit more formal or strict)

Among these, Please remain quiet matches 保持 especially well, because 保持 emphasizes continuing in a state.

So if you want a very close translation, Please remain quiet is excellent.
If you want the most natural everyday English, Please keep quiet or Please be quiet also works well.

In Chinese, commands and requests do not need an exclamation mark to sound like commands.

A sentence like 请保持安静。 with a full stop is completely normal and often looks more polite, neutral, and official.

If you wrote:

• 请保持安静！

it would feel more forceful or emphatic.

So:

• 。 = neutral, standard, formal
• ！ = stronger, more urgent, more emotional

For signs and announcements, 。 is often the more natural choice.

It can be used in conversation, but it sounds more formal than everyday speech.

In real conversation, people often choose softer or more casual alternatives, such as:

• 请安静一下。 = Please be quiet for a moment.
• 请小声一点。 = Please speak a little more softly.
• 安静一点，好吗？ = Be a little quieter, okay?

But if a teacher, staff member, host, or announcer says 请保持安静, it sounds completely natural.

So it is not only for signs, but it definitely has a formal, public-service feel.