bǎochí zhèlǐ gānjìng.

保持 means to keep, maintain, or preserve a state. In this sentence, it means keeping this area in a clean condition.

It is very common in instructions and signs, for example:

• 保持安静 = keep quiet
• 保持距离 = keep a distance
• 保持清洁 = keep clean

Yes. This is an instruction or command, the kind of thing you would see on a sign.

Chinese often leaves out the subject when it is obvious. In a sign, the understood subject is basically everyone reading this. So the sentence does not need to say 你 or 你们.

If you want to make it sound more polite, you can add 请:

• 请保持这里干净。

In Chinese, location words like 这里 can often work a bit like noun phrases. So 这里 can mean both here and this place / this area, depending on context.

In this sentence, 保持这里干净 is understood as keep this place clean or keep this area clean, not the awkward English-style keep here clean.

A useful pattern is:

保持 + place/thing + adjective

So here:

• 保持 = keep / maintain
• 这里 = this place / this area
• 干净 = clean

So the structure is basically keep + this place + clean, which is very close to English.

You can compare:

• 保持房间整洁。 = Keep the room tidy.
• 保持桌面干净。 = Keep the desktop clean.

Because 这里 itself already works well as this place / this area here. You do not need 的.

If you say 这里的干净, that changes the meaning. It would mean something more like the cleanliness of this place, which is a more abstract noun phrase and does not fit this instruction naturally.

So:

• 保持这里干净 = keep this place clean
• 这里的干净 = the cleanliness of this place

Those are not the same structure.

Because 干净 here is the state you are supposed to maintain, not a normal descriptive sentence like 这里很干净.

Compare:

• 这里很干净。 = This place is very clean.
• 保持这里干净。 = Keep this place clean.

If you say 保持这里很干净, it sounds unnatural, because 很 is not normally used in this kind of instruction.

Mostly keep it clean.

保持 focuses on maintaining a state. It suggests that the place should remain clean, or be kept clean continuously.

If you want to emphasize make it clean or clean it up, other verbs are more natural, such as:

• 把这里弄干净。 = Make this place clean.
• 把这里打扫干净。 = Clean this place up.

So 保持 is about maintenance, not the initial cleaning action.

Yes. 这里 and 这儿 both mean here.

The difference is mainly style and regional preference:

• 这里 sounds a little more neutral and works well in writing
• 这儿 sounds more conversational and is common in spoken Mandarin, especially in northern speech

So 保持这儿干净 is understandable, but 保持这里干净 is more likely on a sign.

Yes, it is understandable and natural enough. But depending on the setting, some versions are even more common.

For example:

• 请保持这里干净。 = Please keep this area clean.
• 请保持此处清洁。 = Please keep this area clean.
• 请保持环境整洁。 = Please keep the environment tidy.

Among these, 此处清洁 sounds more formal and sign-like, while 这里干净 sounds more direct and everyday.

They are related, but not identical:

• 干净 = clean, not dirty; very common in everyday speech
• 清洁 = clean / cleanliness; a bit more formal
• 整洁 = neat and tidy, not messy

So on a sign:

• 保持这里干净 focuses on cleanliness
• 保持此处清洁 sounds more formal
• 保持环境整洁 suggests both clean and orderly surroundings

Yes, and it is very common:

• 请保持这里干净。

Adding 请 makes the tone more polite, but the grammar stays the same. It is still an instruction.

Many signs omit 请 to sound shorter and more direct, but both versions are correct.

It is basically an adjective meaning clean.

In Chinese, adjectives often behave more flexibly than in English. After a verb like 保持, the adjective shows the state that should be maintained.

So in 保持这里干净, 干净 tells you the condition that 这里 should stay in.