bié tōu biéren de dōngxi.

Here 别 means don’t and is used to make a negative command.

So:

• 偷 = steal
• 别偷 = don’t steal

This is a very common pattern in Mandarin:

• 别说话。 = Don’t talk.
• 别走。 = Don’t go.
• 别看。 = Don’t look.

The two 别 are doing different jobs:

1. The first 别 means don’t.
2. In 别人, the 别 is part of the word 别人, which means other people or someone else.

So:

• 别偷 = don’t steal
• 别人 = other people / other people’s

Even though the same character appears twice, the meanings are different in this sentence.

别人 means other people or someone else.

Examples:

• 别人说什么？ = What are other people saying?
• 不要管别人。 = Don’t worry about other people.
• 别人的书 = someone else’s book / other people’s books

In your sentence, 别人 refers to the people who own the things.

的 is the common particle used to show possession or attribution, similar to ’s or of in English.

So:

• 别人 = other people
• 别人的 = other people’s / someone else’s
• 别人的东西 = other people’s things

This structure is very common:

• 我的书 = my book
• 他的车 = his car
• 老师的话 = the teacher’s words
• 别人的东西 = other people’s stuff

Normally, no. In this sentence, 的 should stay.

别人东西 sounds unnatural because 别人 is being used to modify 东西, and Mandarin usually needs 的 there.

Compare:

• 我的书 = my book
• 他的手机 = his phone
• 别人的东西 = other people’s things

Sometimes 的 can be omitted in certain close, fixed relationships, like:

• 我妈 = my mom
• 他老师 is not normally correct; you would usually say 他的老师

So for this sentence, 别人的东西 is the natural form.

In this sentence, 东西 means thing, stuff, or belongings.

Yes, the characters literally are:

• 东 = east
• 西 = west

But together, 东西 is a very common word meaning thing(s) or stuff.

Examples:

• 这是什么东西？ = What is this thing?
• 我的东西呢？ = Where is my stuff?
• 别碰我的东西。 = Don’t touch my things.

So here, 别人的东西 means other people’s things / belongings.

Mandarin usually follows Subject–Verb–Object order, much like English.

If we add an implied subject, the sentence is basically:

• (你) 别 偷 别人的 东西。
• (You) don’t steal other people’s things.

Breakdown:

• 别 = don’t
• 偷 = steal
• 别人的东西 = other people’s things

So the verb 偷 comes before the thing being stolen, just as in English.

Not only. 偷 often means to steal, but it can also suggest doing something secretly or on the sly.

For example:

• 偷钱 = steal money
• 偷看 = peek / look secretly
• 偷听 = eavesdrop
• 偷笑 = giggle secretly

In your sentence, because the object is 别人的东西, 偷 clearly means to steal.

Yes, it is very natural and idiomatic.

别偷别人的东西。 is a simple, direct way to say:

• Don’t steal other people’s things.
• Don’t take things that belong to others.

It sounds like something a parent, teacher, or authority figure might say.

It sounds like a direct instruction or warning.

It is not rude by itself, but it is firm. The tone depends on context and voice.

Compare:

• 别偷别人的东西。 = Don’t steal other people’s things.
  Direct and clear.
• 不要偷别人的东西。 = Do not steal other people’s things.
  Also common; can sound slightly more formal or emphatic.
• 不要拿别人的东西。 = Don’t take other people’s things.
  Sometimes softer or broader, because 拿 means take, not specifically steal.

This is an important difference:

• 偷 = steal, take secretly, take unlawfully
• 拿 = take, pick up, hold, get

So:

• 别偷别人的东西 = Don’t steal other people’s things.
• 别拿别人的东西 = Don’t take other people’s things.

The second sentence can be broader. It might mean:

• don’t touch them,
• don’t pick them up,
• don’t take them without permission.

But 偷 specifically focuses on stealing.

Yes. In this word, 东西 is usually pronounced dōngxi, with the second syllable in a neutral tone.

So not usually dōngxī in everyday speech, but more like:

• dōngxi

That neutral tone is very common in everyday Mandarin for this word.

别人 is pronounced biérén:

• 别 = second tone
• 人 = second tone

So both syllables rise.

Be careful not to confuse:

• bié in 别偷 = don’t
• bié in 别人 = part of the word other people

They sound the same, but the meaning depends on the word and context.

Not really in natural English.

Because 偷 with 别人的东西 strongly means steal. The intended sense is clearly:

• Don’t steal other people’s things.

If 偷 is used with an action word, then it may mean secretly do something:

• 偷看别人的东西 = secretly look at other people’s things
• 偷听别人说话 = secretly listen to others talking

But here, with 东西 as the object, 偷 means steal.