qǐng xiān zài dēngjìdān shàng xiě míngzi.

请 is often used to make a request polite, similar to please in English.

In this sentence, 请先在登记单上写名字。 means something like Please write your name on the registration form first.

A few useful notes:

• 请 + verb is a very common polite pattern.
• It can sound like a direct instruction, but still polite.
• In spoken Chinese, the subject you is often omitted when it is obvious.

So the full idea is really:

• (你)请先在登记单上写名字。
• Please first write your name on the registration form.

先 means first.

It tells you that this action should happen before some other action, even if that second action is not said explicitly.

In 请先在登记单上写名字。, 先 comes before the place phrase and the verb:

• 请 + 先 + 在登记单上 + 写名字

This is a very common position for 先:

• 请先坐。 — Please sit down first.
• 你先吃。 — You eat first.
• 我们先回家。 — Let’s go home first.

So here, 先 modifies the action 写名字.

在登记单上 means on the registration form.

This is a very common structure in Chinese:

• 在 + place/location + verb
• or more specifically here,
• 在 + noun + 上 + verb

The word 上 literally means on / on top of / on the surface of. With paper, forms, tables, walls, and other surfaces, Chinese often uses 上 to show where something is written or happens.

Examples:

• 在纸上写字 — write characters on paper
• 在黑板上写 — write on the blackboard
• 在桌子上放书 — put a book on the table

So:

• 登记单 = registration form
• 登记单上 = on the registration form
• 在登记单上写名字 = write your name on the registration form

Chinese usually puts location phrases before the main verb, not after it like English often does.

So Chinese prefers:

• 在登记单上写名字

rather than:

• 写名字在登记单上 ❌

A simple pattern is:

• Subject + 在 + place + verb + object

For example:

• 我在纸上写字。 — I write characters on the paper.
• 他在黑板上画画。 — He draws on the blackboard.

English often puts the place later:

• Write your name on the form.

But Chinese commonly places it before the verb:

• 在登记单上写名字

That is one of the most important word-order differences for English speakers to notice.

登记单 means registration form or registration sheet.

It is made up of:

• 登记 = to register
• 单 = form, sheet, slip, list

So 登记单 is literally something like registration sheet.

You may also see related words such as:

• 表 in 表格 / 申请表 for forms
• 名单 for a name list
• 账单 for a bill

In this sentence, 登记单 is just the document where someone writes their information.

Chinese often leaves out words that are obvious from context.

Here, if someone hands you a form and says:

• 请先在登记单上写名字。

it is naturally understood as:

• Please write your name on the registration form first.

Chinese does not always need to say your when the situation makes it clear.

You could say:

• 请先在登记单上写你的名字。

That is also correct, and it is a bit more explicit. But in real-life instructions, the shorter version is very common.

This kind of omission happens a lot in Chinese:

• 抬手。 — Raise your hand.
• 闭眼。 — Close your eyes.
• 签名。 — Sign your name.

名字 is the common everyday word for name.

• 名字 = name, usually in normal conversation
• 姓名 = full name, more formal, often seen on forms and documents

In this sentence, 写名字 sounds natural and conversational.

If you are dealing with a more formal written instruction, you might also see:

• 请先在登记单上写姓名。

That sounds more official, because 姓名 is commonly used in paperwork.

So both can appear, but:

• 名字 = everyday and natural
• 姓名 = formal and document-style

Chinese often omits the subject when it is obvious.

In this situation, the speaker is clearly talking to the person being asked to fill out the form, so 你 is understood without being said.

So this sentence is effectively:

• (你)请先在登记单上写名字。

This is very normal in commands, instructions, and everyday conversation.

Examples:

• 请坐。 — Please sit.
• 先吃饭。 — Eat first.
• 往左走。 — Go left.

English usually needs a subject less often in commands too, but Chinese goes even further in leaving out anything obvious from context.

Yes. 请 has more than one common meaning.

It can mean:

1. please / to politely ask someone to do something
2. to invite
3. to treat someone (for example, paying for a meal)

In this sentence, it clearly means please because it is followed by an action:

• 请先在登记单上写名字。
• Please first write your name on the registration form.

Other examples:

• 我请你吃饭。 — I’m treating you to a meal.
• 请他来。 — Invite him to come.
• 请进。 — Please come in.

So you must use context to know which meaning is intended.

The pinyin given is:

• 登记单 — dēngjìdān
• 名字 — míngzi

A few pronunciation notes:

• 登 dēng = first tone
• 记 jì = fourth tone
• 单 dān = first tone
• 名 míng = second tone
• 字 zi = usually neutral tone here, so it is lighter and shorter

So 名字 is usually pronounced more like:

• míng·zi

not with a strong full third or fourth syllable.

Also, in connected speech, the whole sentence should sound fairly smooth:

• Qǐng xiān zài dēngjìdān shàng xiě míngzi.

Try not to stress every syllable equally. Usually the key information gets a bit more emphasis:

• 请先 ...
• 登记单上
• 写名字

Yes, absolutely. That is a very natural alternative.

• 请先在登记单上写名字。
• 请先把名字写在登记单上。

Both mean basically the same thing:

• Please write your name on the registration form first.

The difference is in structure:

1. 在登记单上写名字

   • location before the verb
   • very straightforward and common

2. 把名字写在登记单上

   • uses the 把 construction
   • puts focus on what is being written: the name
   • often used when talking about disposing of or placing something somewhere through an action

So:

• 在登记单上写名字 = write your name on the form
• 把名字写在登记单上 = take your name and write it onto the form

Both are correct, but the original version is simpler and especially good for learners.

It is best described as polite and neutral.

Because it starts with 请, it is courteous. At the same time, the sentence is short and practical, which makes it sound like a normal instruction you might hear:

• at a reception desk
• in a clinic
• at a hotel
• at an office
• during event check-in

It is not especially casual, but not overly formal either.

If you wanted to sound more formal or service-oriented, you might hear:

• 请您先在登记单上写一下名字。
• 麻烦您先在登记单上填写姓名。

If you wanted to sound simpler and more direct:

• 先写名字。

So the original sentence sits in the middle: polite, standard, and very usable in real life.