Zachowanie jest ważne.

Here, zachowanie means behavior, conduct, or the way someone acts.

It is a common Polish noun used for both:

• a person’s general behavior
• behavior in a particular situation

So Zachowanie jest ważne means Behavior is important or Conduct is important.

Because zachowanie is a neuter noun in Polish.

In Polish, adjectives must agree with the noun in:

• gender
• number
• case

So:

• ważny = masculine singular
• ważna = feminine singular
• ważne = neuter singular

Since zachowanie is neuter, the correct form is ważne.

A very common clue is the ending -e or -o in the dictionary form of a noun.

Zachowanie ends in -e, and nouns of this type are typically neuter.

So:

• to zachowanie = this behavior
  not
• ten zachowanie
• ta zachowanie

The correct demonstrative is to, which also shows it is neuter.

Jest means is.

It is the 3rd person singular form of być = to be.

So the sentence is structured like this:

• Zachowanie = behavior
• jest = is
• ważne = important

Together: Behavior is important.

Normally, no in this sentence.

In present-tense Polish, być is usually expressed when it means is/am/are in a sentence like this. So:

• Zachowanie jest ważne. = correct

Leaving out jest here would sound incomplete or unnatural in standard Polish.

Not completely. Polish word order is fairly flexible.

The most neutral version is:

• Zachowanie jest ważne.

But you may also see:

• Ważne jest zachowanie.

This second version is more marked and can sound more emphatic, something like:

• What is important is behavior or
• Behavior is what matters

So the original sentence is the most straightforward and natural basic form.

A rough English-friendly guide is:

• zachowanie ≈ za-ho-VA-nye
• jest ≈ yest
• ważne ≈ VAZH-ne

A few important details:

• ch sounds like the ch in Scottish loch or German Bach
• j sounds like English y
• ż sounds like the s in measure
• the stress is usually on the second-to-last syllable

So:

• za-cho-WA-nie
• WAŻ-ne

It can mean behavior in general, not just good manners.

Depending on context, zachowanie can refer to:

• social behavior
• a child’s behavior
• someone’s conduct
• behavior in psychology or science

So it is broader than just manners, though in some contexts it can certainly refer to how well someone behaves.

Usually, yes.

Ważny / ważna / ważne most often means:

• important
• significant
• of importance

So in this sentence, ważne is a very natural translation of important.

It is in the nominative case.

That is because zachowanie is the subject of the sentence:

• Zachowanie = the thing being talked about

In a basic X is Y sentence, the subject is normally in the nominative.

Yes. It is related to the verb zachować (się).

Very roughly:

• zachować się = to behave
• zachowanie = behavior

This is useful because Polish often forms nouns from verbs in this way.

So if you know:

• On źle się zachowuje. = He behaves badly.

then zachowanie as behavior will feel easier to remember.

Yes, it can, depending on context.

Polish does not use articles like a or the, so:

• Zachowanie jest ważne.

can mean:

• Behavior is important or
• The behavior is important

Context tells you which meaning is intended. Out of context, English speakers often translate it as the more general Behavior is important.

You would say:

• To zachowanie jest ważne.

Here:

• to = this
• zachowanie = behavior
• jest ważne = is important

That makes it specific, instead of general.