Muž krmí kočku.

Because kočku is the accusative singular form of kočka.

In this sentence, the cat is the direct object, so Czech uses the accusative case. Many feminine nouns ending in -a change to -u in the accusative singular:

• kočka = nominative
• kočku = accusative

So kočka is the dictionary form, but kočku is the correct form in this sentence.

Because muž is the subject of the sentence, so it is in the nominative case.

Its nominative singular form is muž, which is also the dictionary form. So unlike kočka, it does not need to change here.

Czech shows this mainly through case endings.

• muž is in the nominative case, which marks the subject
• kočku is in the accusative case, which marks the direct object

So the endings tell you who is doing the action and who is receiving it.

Krmí is the 3rd person singular present tense of the verb krmit.

So it means:

• he feeds
• she feeds
• it feeds

In this sentence, it matches muž, so the subject is he / the man.

It can mean either, depending on context.

Czech present tense often covers both:

• feeds
• is feeding

Also, krmit is an imperfective verb, so it naturally describes an ongoing action or a repeated/habitual one.

Czech does not use articles like English does.

So:

• muž can mean a man or the man
• kočku can mean a cat or the cat

The exact meaning comes from context, not from a separate word like a or the.

Yes. Czech word order is more flexible than English because case endings show the grammatical roles.

Muž krmí kočku is the most neutral word order. But you could also say:

• Kočku krmí muž.
• Muž kočku krmí.

These are still grammatical, but they change the emphasis or focus.

The dictionary forms are:

• muž — masculine animate noun
• krmit — infinitive of the verb
• kočka — feminine noun

Gender matters in Czech because it affects endings, declension, and agreement.

A rough guide is:

• muž — the ž sounds like the s in measure
• krmí — the í is a long ee sound
• kočku — the č sounds like ch in church

A very rough English-style approximation would be moozh kr-mee koch-koo, but Czech pronunciation is tighter than that spelling suggests. One extra thing to notice is that Czech r is pronounced clearly, even in a consonant-heavy word like krmí.