Przedsiębiorca wyjaśnia pomyłkę.

Because it is the direct object of the verb wyjaśnia.

In Polish, a feminine noun like pomyłka changes form in the accusative singular, which is the case typically used for a direct object.

• nominative: pomyłka
• accusative: pomyłkę

So:

• Pomyłka jest poważna. = The mistake is serious.
  Here pomyłka is the subject, so it stays in the nominative.
• Przedsiębiorca wyjaśnia pomyłkę.
  Here pomyłkę is what is being explained, so it takes the accusative.

Wyjaśnia is the 3rd person singular present tense form of wyjaśniać.

It means:

• he explains
• she explains
• it explains
• or, depending on context, is explaining

Polish does not need a separate word for he/she/it here, because the verb ending already shows the person and number.

A few present-tense forms of wyjaśniać:

• ja wyjaśniam = I explain / am explaining
• ty wyjaśniasz = you explain
• on/ona/ono wyjaśnia = he/she/it explains
• my wyjaśniamy = we explain
• wy wyjaśniacie = you all explain
• oni/one wyjaśniają = they explain

It can mean either, depending on context.

Polish present tense often covers both the simple present and the present continuous in English.

So wyjaśnia could be understood as:

• explains
• is explaining

The larger context tells you which is more natural.

For example:

• Przedsiębiorca wyjaśnia pomyłkę w oświadczeniu.
  Could mean The entrepreneur explains the mistake in the statement.
• In a live situation, it might mean The entrepreneur is explaining the mistake right now.

Because Polish has no articles like English a/an/the.

So:

• przedsiębiorca can mean an entrepreneur or the entrepreneur
• pomyłkę can mean a mistake or the mistake

The exact meaning depends on context.

This is very normal in Polish. You usually understand definiteness from the situation, previous sentences, or word order/emphasis.

Yes — and that is exactly what happens in this sentence.

Polish is a language where the subject pronoun is often omitted, because the verb ending already gives enough information.

So instead of saying:

• On wyjaśnia pomyłkę. = He is explaining the mistake.

Polish often simply says:

• Wyjaśnia pomyłkę.

In your sentence, the subject is not omitted because it is stated explicitly as przedsiębiorca.

But if the subject were already clear from context, Polish could drop it.

Grammatically, przedsiębiorca is a masculine noun. In this sentence, it most naturally refers to a male entrepreneur.

For a specifically female entrepreneur, Polish often uses:

• przedsiębiorczyni

So you may see:

• Przedsiębiorca wyjaśnia pomyłkę. = a male entrepreneur explains the mistake
• Przedsiębiorczyni wyjaśnia pomyłkę. = a female entrepreneur explains the mistake

One thing that can confuse learners is that przedsiębiorca ends in -a, which often looks feminine. But there are several masculine nouns in Polish with -a endings, especially for professions or roles, such as:

• mężczyzna = man
• kolega = male friend / colleague

Because not all Polish masculine nouns end in a consonant. Some masculine nouns, especially words referring to people, end in -a.

So although przedsiębiorca looks like a feminine noun at first glance, it is actually masculine animate.

You can see this in agreement patterns, for example with adjectives:

• ten przedsiębiorca = this entrepreneur
  not ta przedsiębiorca

And in past tense:

• Przedsiębiorca wyjaśniał pomyłkę. = The entrepreneur was explaining the mistake.
  The masculine past form wyjaśniał shows the subject is masculine.

The basic word order is:

• Subject + Verb + Object
• Przedsiębiorca wyjaśnia pomyłkę.

This is a very natural neutral order in Polish.

But Polish word order is more flexible than English, because case endings show grammatical function. So you can change the order for emphasis:

• Pomyłkę wyjaśnia przedsiębiorca.
  Emphasis on the mistake
• Wyjaśnia pomyłkę przedsiębiorca.
  More marked, possible in the right context

Even when the order changes, pomyłkę is still the object because of the accusative ending -ę.

These are an aspect pair, which is a very important feature of Polish verbs.

• wyjaśniać = imperfective
• wyjaśnić = perfective

In simple terms:

• wyjaśniać focuses on the process, repetition, or ongoing action
• wyjaśnić focuses on the action as completed

Your sentence uses wyjaśnia from wyjaśniać, so it presents the action as ongoing or general.

Compare:

• Przedsiębiorca wyjaśnia pomyłkę.
  The entrepreneur is explaining / explains the mistake.
• Przedsiębiorca wyjaśni pomyłkę.
  The entrepreneur will explain the mistake.
  Because perfective verbs do not normally have a true present meaning in Polish; their present forms usually refer to the future.

A rough pronunciation guide is:

• Przedsiębiorca ≈ pshet-shyem-BYOR-tsa
• wyjaśnia ≈ vih-YASH-nya
• pomyłkę ≈ po-MIHW-ken

A few sounds that may be tricky:

• rz in przedsiębiorca sounds like Polish ż
• się in przedsiębiorca is pronounced roughly like shyem
• ś in wyjaśnia is a soft sh sound
• ł in pomyłkę sounds like English w
• ę at the end of pomyłkę is often pronounced approximately like -en or a nasal vowel, depending on speech style

You do not need to pronounce every letter exactly as in English spelling. Polish spelling is fairly regular once you learn the sound rules.

They are similar, but not always identical.

• pomyłka often means a mistake, especially a mix-up, slip, or error someone made
• błąd is often a more general error or fault

In many contexts they overlap, but the nuance can differ.

Examples:

• To była pomyłka. = That was a mistake.
• To jest błąd w raporcie. = That is an error in the report.

In your sentence, pomyłkę suggests that the entrepreneur is explaining some kind of mistake or mix-up.