yangpareul yalbge sseoreo juseyo.

Here is the sentence broken down:

• 양파 = onion
• 를 = object particle
• 얇게 = thinly
• 썰어 = slice / cut into slices
• 주세요 = please do for me / please give me the action

So the whole sentence means something like:

• Please slice the onion thinly.
• more naturally in English: Please slice the onion into thin pieces.

를 marks 양파 as the direct object of the verb.

In other words, it tells you that the onion is the thing being sliced.

• 양파를 썰다 = to slice the onion
• 사과를 먹다 = to eat an apple
• 문을 열다 = to open the door

In Korean, object particles like 을/를 are very common, and they help show what the action is happening to.

Because 양파 ends in a vowel, it takes 를 rather than 을.

얇다 is an adjective meaning to be thin. To describe how an action is done, Korean often changes an adjective into an adverb with -게.

So:

• 얇다 = to be thin
• 얇게 = thinly

That means 얇게 썰다 literally means to slice thinly.

This pattern is very common:

• 빠르다 → 빠르게 = quickly
• 조용하다 → 조용하게 = quietly
• 쉽다 → 쉽게 = easily

So 얇게 is not a different word you just have to memorize by itself; it follows a common grammar pattern.

Both can relate to cutting, but they are not exactly the same.

• 자르다 = to cut, in a broad general sense
• 썰다 = to slice, especially food, into pieces

So for cooking, 썰다 is often the more natural verb when talking about onions, carrots, meat, and so on.

Examples:

• 양파를 썰다 = to slice an onion
• 고기를 썰다 = to slice meat
• 종이를 자르다 = to cut paper
• 머리를 자르다 = to cut hair

In this sentence, 썰다 is used because slicing an onion is a food-preparation action.

Both are requests, but they feel a little different.

• 썰어 주세요 = please slice it
• 썰세요 = slice it, please / please slice it

-아/어 주세요 is very common when asking someone to do something for you. It often sounds a bit warmer or more natural in everyday situations.

So 양파를 얇게 썰어 주세요 sounds like a normal polite request, especially in cooking instructions or when speaking to someone helping you.

By itself, 주다 means to give. But in grammar like -아/어 주세요, it works as a helper verb meaning something like:

• please do this
• please do this for me

So 썰어 주세요 is not literally give slicing in natural English. It is a polite request formula.

You will see this pattern everywhere:

• 도와주세요 / 도와 주세요 = please help me
• 기다려 주세요 = please wait
• 앉아 주세요 = please sit down

The subject is omitted, which is very normal in Korean.

Korean often leaves out information that is obvious from context. In this sentence, the speaker is clearly asking the listener to slice the onion, so there is no need to say you.

English usually needs an explicit subject or imperative form, but Korean can often leave it unsaid.

So the sentence is understood as:

• (You,) please slice the onion thinly.

Yes, to some extent. Korean word order is more flexible than English, especially for adverbs and objects, as long as the particles make the roles clear.

These are all possible:

• 양파를 얇게 썰어 주세요.
• 얇게 양파를 썰어 주세요.

The first one is the most neutral and natural.

Because 를 marks 양파 as the object, the meaning stays clear even if the order changes. Still, not every order sounds equally natural, so learners should usually stick with the standard pattern until they get used to Korean rhythm.

Not exactly.

• 얇게 = thinly, in thin slices
• 잘게 = finely, into small pieces

So:

• 양파를 얇게 썰어 주세요 = please slice the onion thinly
• 양파를 잘게 썰어 주세요 = please chop the onion finely

This is an important difference in cooking Korean. 얇게 focuses on thickness, while 잘게 focuses on small size.

You will see both 썰어 주세요 and 썰어주세요 in real life.

Traditionally, when 주다 is used as an auxiliary verb after -아/어, it is often spaced:

• 썰어 주세요

But in everyday writing, many people write it 붙여서 as:

• 썰어주세요

For learners, it is good to recognize both. If you want to follow careful standard spacing, 썰어 주세요 is a safe choice.

Here are some common levels:

• 양파를 얇게 썰어 줘. = casual, to a close friend or someone younger
• 양파를 얇게 썰어 주세요. = polite everyday request
• 양파를 얇게 썰어 주십시오. = more formal / stiff

So 주세요 is a very useful middle level: polite, common, and natural in many situations.

썰어 comes from 썰다.

In speech, it sounds roughly like:

• 써러

That is because the ㄹ is carried into the next syllable when the ending is added.

So:

• 썰다 sounds roughly like 썰다
• 썰어 sounds roughly like 써러

You do not need to force a separate English-style r sound; just say it the Korean way with the ㄹ sound flowing smoothly.