Liják začal večer.

Začal is the past tense form of začít, which means to begin / to start.

It is:

• singular
• masculine
• 3rd person

In Czech past tense, the verb agrees with the subject in gender and number, so začal matches liják, which is a masculine singular noun.

Because liják is a masculine noun.

Past tense forms change like this:

• začal = masculine singular
• začala = feminine singular
• začalo = neuter singular

Since liják is masculine singular, začal is the correct form.

Czech does not have articles. There is no direct equivalent of English a/an or the.

So liják can mean:

• a downpour
• the downpour

The exact English choice depends on context, not on a separate Czech word.

In Czech, some time expressions are used without a preposition, and večer is one of them.

So:

• večer = in the evening / one evening
• ráno = in the morning
• v noci = at night uses a preposition, so not all time expressions behave the same way

Here, večer is the normal and natural way to say in the evening.

For a learner, the easiest answer is: here it functions like an adverb of time.

The form večer is also the noun evening, but in this sentence it tells us when the action happened: in the evening.

So in practice, read it as a time expression, not as the subject or object.

Because začal is perfective, and Czech normally uses the perfective verb when talking about a single completed event such as the moment something began.

• začal = started / began
• začínal = was starting / used to start / started repeatedly, depending on context

In this sentence, the speaker is treating the beginning of the downpour as one finished event, so začal is the natural choice.

Yes. Czech word order is fairly flexible.

Liják začal večer. is a normal sentence, with the time expression at the end.

You could also say:

• Večer začal liják.

That would put more emphasis on when it happened. The basic meaning stays very similar, but the focus changes.

A simple pronunciation guide is:

• Liják ≈ LI-yaak
• začal ≈ ZA-chal, where č sounds like ch in church
• večer ≈ VE-cher, again with č like ch in church

Czech stress is usually on the first syllable of each word:

• LIják
• ZAčal
• VEčer