Họ trộm điện thoại.

Here, họ means they.

Vietnamese pronouns do not change for subject/object the way English does, so họ can mean they when it is the subject of the sentence.

Also, họ does not show gender, so it can mean:

• they for a group of men
• they for a group of women
• they for a mixed group

It is generally a fairly neutral written/spoken way to say they.

Yes. This sentence follows the basic Subject – Verb – Object pattern:

• Họ = subject
• trộm = verb
• điện thoại = object

So the structure is:

Họ trộm điện thoại.
→ They steal/stole a phone / phones.

That makes this sentence fairly straightforward for an English speaker.

In this sentence, trộm is being used as a verb, meaning to steal.

So:

• trộm điện thoại = steal a phone / steal phones

Be aware that trộm can appear in other expressions too, and words in Vietnamese often have flexible uses depending on context. But in this sentence, the simplest reading is clearly verbal: to steal.

Vietnamese does not use articles the way English does.

So điện thoại can mean:

• a phone
• the phone
• phones
• mobile phones / telephones in a general sense

The exact meaning depends on context.

If Vietnamese needs to be more specific, it can add other words, for example:

• một cái điện thoại = a phone
• cái điện thoại đó = that/the phone
• những cái điện thoại = phones

But in a short sentence like Họ trộm điện thoại, leaving that unspecified is completely normal.

By itself, điện thoại does not clearly mark singular or plural.

So this sentence could mean:

• They stole a phone
• They stole the phone
• They steal phones
• They stole phones

Vietnamese often leaves number unmarked unless it matters.

If you want to make plurality clearer, Vietnamese can use markers such as:

• những điện thoại or more naturally with a classifier
• nhiều điện thoại = many phones

But in everyday Vietnamese, number is often understood from context rather than grammar.

Vietnamese verbs do not change form for tense the way English verbs do.

So trộm can mean:

• steal
• stole
• are stealing
• have stolen

depending on context.

Time is usually shown by:

• context
• time words like hôm qua (yesterday), bây giờ (now), ngày mai (tomorrow)
• aspect markers such as đã, đang, sẽ

For example:

• Họ đã trộm điện thoại. = They stole / have stolen the phone.
• Họ đang trộm điện thoại. = They are stealing the phone.
• Họ sẽ trộm điện thoại. = They will steal the phone.

Without extra context, the sentence is tense-neutral.

Not in this sentence.

Classifiers are common in Vietnamese when a noun is being counted or specifically identified, but they are not always required.

For example:

• một cái điện thoại = one phone / a phone
• cái điện thoại này = this phone

But after a verb, a bare noun like điện thoại is very natural:

• mua điện thoại = buy phone(s)
• bán điện thoại = sell phone(s)
• trộm điện thoại = steal phone(s)

So Họ trộm điện thoại is grammatically fine without a classifier.

No. Vietnamese has several ways to refer to they, depending on context, relationship, and style.

For example:

• họ = a neutral they, often used in writing or when speaking somewhat generally
• bọn họ = they / that group
• tụi nó = they, but informal and can sound dismissive depending on context
• các anh ấy / các cô ấy / họ = more specific possibilities in context

So họ is correct here, but it is not the only option.

Normally, no. In this sentence, the most natural reading is verbal:

• Họ = subject
• trộm = verb
• điện thoại = object

So it is understood as They steal phones or They stole the phone.

If you wanted to say They are thieves, Vietnamese would usually phrase it differently, such as:

• Họ là kẻ trộm. = They are thieves.
• Họ là trộm is less standard/natural than using kẻ trộm or another noun phrase.

Both are possible, but they are not exactly the same in tone and usage.

• trộm can function as a verb meaning steal
• ăn trộm is a very common everyday expression meaning to steal

So learners will often hear:

• Họ ăn trộm điện thoại. = They steal/stole phones.

Your sentence Họ trộm điện thoại is understandable and grammatical, but ăn trộm may sound more common in everyday speech in many contexts.

trộm is pronounced with:

• the tr consonant, which in standard Vietnamese is a retroflex/ch-like sound for many speakers
• the vowel ộ, a short ô-type vowel with a heavy falling glottalized tone
• final m

The tone is important. The mark on ộ shows the nặng tone, which is low and cut short.

A rough learner-friendly approximation is something like chohm with a very short, heavy, low tone, but the real Vietnamese pronunciation is more precise than English spelling can show.

điện thoại can mean telephone in general, but in modern everyday usage it often refers to a phone, very often a mobile phone, depending on context.

So in many real-life situations, Họ trộm điện thoại would likely be understood as:

• They stole a phone
• often specifically a mobile phone

If speakers want to be more specific, they can say:

• điện thoại di động = mobile phone
• điện thoại bàn = landline phone

Yes.

Because Vietnamese does not mark tense on the verb, Họ trộm điện thoại can describe:

• a general habit: They steal phones
• a present situation: They are stealing phones
• a past event: They stole the phone

Context decides which reading is intended.

For example:

• Họ thường trộm điện thoại ở chợ. = They often steal phones at the market.
  This clearly shows a habit.
• Hôm qua họ trộm điện thoại của tôi. = Yesterday they stole my phone.
  This clearly shows a past event.