tā tōu le wǒ de shǒujī.

The structure is:

他 + 偷 + 了 + 我的手机
subject + verb + aspect particle + object

So Mandarin is following the normal Subject–Verb–Object pattern here, just like English:

• 他 = he
• 偷 = steal
• 了 = marks the action as completed
• 我的手机 = my phone

Here, 了 shows that the action is completed.

So 偷了 means something like:

• stole
• has stolen
• did steal

It does not simply mean past tense in the same way English does. It marks the event as a completed whole. In this sentence, that completed action is naturally understood as He stole my phone.

No. 了 is mainly an aspect marker, not a pure past-tense marker.

That means it tells you about the state of the action rather than just when it happened. In this sentence, because stealing the phone is a completed event, English usually translates it as past: stole.

So a good way to think of it is:

• past tense = a time idea
• 了 = a completion idea

Very often those overlap, but they are not exactly the same thing.

的 links 我 and 手机 and shows possession.

So:

• 我 = I / me
• 我的 = my
• 我的手机 = my phone

You can think of 的 as doing the job of English -’s or of, depending on context. Here it is the standard possessive pattern:

pronoun + 的 + noun

Normally, no in standard Mandarin.

With a pronoun like 我, you usually say:

• 我的手机 = my phone

not:

• 我手机

There are some special cases in Mandarin where 的 can be omitted, especially in close relationships or set expressions, but with 我 + 手机, the normal form is 我的手机.

Because 我的手机 is the object of 偷.

Mandarin usually puts the object after the verb:

• 他偷了我的手机
• literally: He stole my phone

The whole phrase 我的手机 stays together as one noun phrase. You do not separate 我 from 手机.

No. In Mandarin, 他 and 她 are both pronounced tā.

So:

• 他 = he
• 她 = she

They sound the same in speech. The difference is only visible in writing. In your sentence, because the character is 他, it specifically means he.

Here, 了 is pronounced le with a neutral tone.

So you say:

• tā tōu le wǒ de shǒujī

This is not the liǎo pronunciation of 了, which appears in other words or structures. In this sentence, it is the very common aspect-particle le, said lightly.

In this sentence, 偷 means to steal.

So 偷了我的手机 means stole my phone.

It is worth knowing that 偷 can also appear in other contexts where it means secretly doing something, such as:

• 偷看 = peek / look secretly
• 偷听 = eavesdrop / listen secretly

But in 偷了我的手机, with a thing as the object, the meaning is clearly steal.

Usually 手机 means a mobile phone / cell phone, not just any phone in general.

So in modern Chinese, 手机 is specifically a cell phone. If you want to talk about a landline, you would usually use another word, such as 座机.

That is why 我的手机 is best understood as my cell phone / my mobile phone.

The dictionary tones are:

• 他 tā = first tone
• 偷 tōu = first tone
• 了 le = neutral tone
• 我 wǒ = third tone
• 的 de = neutral tone
• 手 shǒu = third tone
• 机 jī = first tone

In natural speech:

• 我 in 我的 is often pronounced as a low, shortened third tone
• 手 before 机 is also often not a full dipping third tone

So learners should not try to over-pronounce every third tone. The sentence should sound smooth and connected.

Yes. The original sentence is completely natural, but Mandarin also allows other versions depending on what you want to emphasize.

For example:

• 我的手机被他偷了。 = My phone was stolen by him.
  This focuses on the phone.

• 他把我的手机偷了。 = He stole my phone.
  This can sound a little more pointed or result-focused.

But 他偷了我的手机。 is a very normal and straightforward way to say it.

Yes. 他偷了我的手机。 is a direct statement of fact: He stole my phone.

If you are not completely sure, Mandarin speakers often soften it, for example:

• 我怀疑他偷了我的手机。 = I suspect he stole my phone.
• 我的手机好像被他拿走了。 = It seems like he took my phone.

So the original sentence sounds confident and accusatory, not hesitant.