Svědek popsal neznámého zloděje.

Because svědek is in the nominative singular, which is the normal case for the subject of a Czech sentence.

In Svědek popsal neznámého zloděje:

• svědek = nominative singular = the witness
• neznámého zloděje = accusative singular = the unknown thief

So the structure is:

• Svědek = the person doing the action
• popsal = described
• neznámého zloděje = the person being described

Even though English relies heavily on word order, Czech often shows these roles through case endings instead.

This is because zloděj is a masculine animate noun, and in Czech, the accusative singular of masculine animate nouns usually looks like the genitive singular.

So:

• zloděj = nominative singular
• zloděje = accusative singular

And the adjective matches it:

• neznámý = nominative singular masculine
• neznámého = accusative singular masculine animate

So neznámého zloděje is a matching adjective + noun pair in the accusative singular.

It is singular: an/the unknown thief.

This can be confusing because forms like zloděje may look plural to learners. But here it is singular because:

• neznámého is singular masculine animate accusative
• zloděje matches that pattern

So the sentence is about one thief, not several.

Czech has no articles, so it does not use separate words like a, an, or the.

That means:

• svědek can mean a witness or the witness
• neznámého zloděje can mean an unknown thief or the unknown thief

Which one is meant depends on context. In many translations, English has to choose an article even when Czech leaves it open.

Popsal is past tense.

More specifically, it is:

• past tense
• masculine singular form
• from the verb popsat

The masculine singular ending is because the subject svědek is a masculine noun.

Compare:

• popsal = he described / the male witness described
• popsala = she described
• popsalo = it described
• popsali = they described (masculine animate or mixed group)

This is a question of aspect, which is very important in Czech.

• popsat → perfective
• popisovat → imperfective

Popsal suggests a completed action: the witness finished describing the thief.

Popisoval would suggest something more like:

• he was describing him
• he described him repeatedly
• the action is viewed as ongoing or not presented as completed

So Svědek popsal neznámého zloděje presents the description as a finished event.

Yes, here neznámého means unknown / unidentified.

So neznámého zloděje means something like:

• an unknown thief
• an unidentified thief

It does not usually mean that the witness personally did not know him in a social sense, like a thief he had never met before, unless context pushes it that way. In crime-report language, it usually means the thief’s identity is unknown.

Yes. Czech word order is relatively flexible because cases show grammatical roles.

For example, these are possible:

• Svědek popsal neznámého zloděje.
• Neznámého zloděje popsal svědek.
• Svědek neznámého zloděje popsal.

The basic meaning stays similar, but the focus or emphasis changes.

• Svědek popsal neznámého zloděje. = neutral
• Neznámého zloděje popsal svědek. = puts emphasis on the unknown thief
• Svědek neznámého zloděje popsal. = may sound more marked, depending on context

So Czech uses word order more for information structure than English does.

A rough pronunciation guide for an English speaker is:

• Svědek ≈ SVYE-dek
• popsal ≈ POP-sahl
• neznámého ≈ nez-NAA-meh-ho
• zloděje ≈ ZLO-dye-ye

A few helpful notes:

• svě sounds roughly like svye
• á is a long vowel
• ě often softens the preceding consonant and creates a ye/yeh-type sound
• j is pronounced like English y
• Czech stress is normally on the first syllable of each word

So the sentence is stressed roughly as:

SVĚ-dek POP-sal ne-ZNÁ-me-ho ZLO-dě-je

Because the adjective agrees with the noun in:

• gender
• number
• case

Here both are:

• masculine animate
• singular
• accusative

So:

• neznámého = accusative singular masculine animate
• zloděje = accusative singular masculine animate

That agreement tells you they form one noun phrase: the unknown thief / an unknown thief.

The dictionary forms are:

• svědek → svědek = witness
• popsal → popsat = to describe
• neznámého → neznámý = unknown
• zloděje → zloděj = thief

This is useful because Czech words change form a lot. When you meet a sentence form like neznámého or zloděje, it helps to identify the base form first and then work out the case, number, and gender.