يصل القطار حينها.

This sentence uses a very common Arabic word order: verb + subject + adverbial expression.

So:

• يصل = arrives
• القطار = the train
• حينها = then / at that time

In Arabic, starting with the verb is completely normal, especially in Modern Standard Arabic. English usually prefers The train arrives then, but Arabic often prefers Arrives the train then in structure, even though that sounds unnatural in English.

You could also say:

• القطار يصل حينها

This is also grammatical, but it shifts the style slightly and gives more prominence to القطار.

يصل is the imperfect form of the verb وصل.

Here it means:

• he arrives
• it arrives

Since القطار is a masculine singular noun, the verb appears in the 3rd person masculine singular form:

• يصل = he/it arrives

Arabic uses the same form for he and for a masculine singular non-human noun like القطار.

In Arabic, القطار is grammatically masculine singular, so the verb must match that.

That is why you get:

• يصل القطار = the train arrives

If the subject were dual or plural, the verb agreement rules would depend on word order. But here, with a singular masculine subject, يصل is exactly what you expect.

القطار is the subject of the sentence, so in fully vowelled Arabic it would be in the nominative case:

• القطارُ

So the fully vowelled sentence would be:

• يَصِلُ القِطارُ حينَها

In normal unvowelled writing, the case ending is not shown, so you just see القطار.

حينها means then, at that time, or when that happens, depending on context.

It is made of:

• حين = time / moment / when
• ها = her/it, here referring back to a time, situation, or event

So literally it is something like at that time.

In many contexts, it works very naturally as:

• then
• at that point
• at that time

The ها is a pronoun suffix. It refers back to something already understood from the context.

So:

• حين = a time / when
• حينها = its time / at that time / then

In practice, learners should usually understand حينها as a set expression meaning then or at that time.

You may also see similar forms like:

• وقتها = at that time
• بعدها = after that
• قبلها = before that

A careful fully vowelled pronunciation would be:

• يَصِلُ القِطارُ حينَها

A rough pronunciation guide:

• ya-si-lu al-qi-taa-ru ḥii-na-haa

A few notes:

• يصل has a short i in the middle: yaṣilu
• القطار begins with q, a deeper sound than English k
• حينها begins with ḥ, a breathy deeper h sound

It can mean arrives, but the root وصل has a broader idea of reaching or arriving at something.

Depending on context, يصل can mean:

• arrives
• reaches
• gets to

In this sentence, with القطار, the most natural translation is the train arrives.

Yes, حينها is quite natural in Modern Standard Arabic and written Arabic, but it sounds more formal or literary than many everyday spoken alternatives.

In MSA, it is perfectly good.

In spoken dialects, people might use different words for then or at that time, depending on the region. But for MSA study, حينها is a useful and common expression.

Yes, depending on context, the Arabic imperfect يصل can sometimes be understood as present or future.

So يصل القطار حينها could mean:

• The train arrives then
• The train will arrive then

Arabic often relies on context for this. If the speaker wants to make the future especially clear, they might use a future marker such as:

• سيصل القطار حينها = the train will arrive then

Without سـ or سوف, the sentence can still be interpreted as future if the context clearly points that way.