Dane są ważne.

• dane = data
• są = are
• ważne = important

Grammatically:

• dane is the subject
• są is the 3rd person plural form of być (to be)
• ważne is an adjective describing dane

So the structure is basically Subject + are + adjective.

Because in Polish, dane meaning data normally behaves as a plural noun.

That is why you get:

• dane są = data are
• not dane jest

This is different from modern English, where data is often treated as singular in everyday speech. In Polish, dane is grammatically plural.

Not one that is normally used in everyday Polish for a datum or one piece of data.

In practice, if Polish speakers want to refer to a single item, they usually use a different word or a more specific phrase, for example:

• informacja = information / a piece of information
• a more specific noun such as liczba (number), wartość (value), adres (address), etc.

So for ordinary usage, just remember dane as a plural noun.

Because są is the plural form of to be, while jest is singular.

Compare:

• dane są ważne = data are important
• informacja jest ważna = the information is important

Since dane is plural, the verb must also be plural:

• singular subject → jest
• plural subject → są

Polish adjectives must agree with the noun they describe.

Here, dane is:

• plural
• non-masculine-personal

So the adjective must also be in the plural non-masculine-personal form:

• ważne

Compare:

• ważny = singular masculine
• ważna = singular feminine
• ważne = singular neuter or plural non-masculine-personal
• ważni = plural masculine-personal

Since dane is not a group of men or people, ważni would be wrong here.

It is in the nominative plural, because it is the subject of the sentence.

The adjective ważne matches it in the same grammatical pattern. In a sentence with być + adjective, the adjective stays in the agreeing adjective form, so ważne is exactly what you expect here.

No. Polish does not have articles like a and the.

So Dane są ważne can mean:

• Data are important
• The data are important

The exact meaning depends on context.

If you want to make it more specific, you can add a word like te:

• Te dane są ważne = These data are important / This data is important

Yes. Polish word order is more flexible than English word order.

The neutral order is:

• Dane są ważne.

But you can also say:

• Ważne są dane.

That version puts more emphasis on important, or can sound contrastive, as if you mean What matters is the data.

So the basic meaning stays similar, but the emphasis changes.

Normally, no. In standard Polish, the present-tense form of to be is usually expressed.

So the normal sentence is:

• Dane są ważne.

If you say only:

• Dane ważne

it sounds incomplete in normal speech, though it might appear in:

• notes
• headlines
• labels
• very compressed style

For regular sentences, keep są.

You would usually say:

• Te dane są ważne.

Because dane is plural, the demonstrative must also be plural:

• te = these

So even if English says this data, Polish still uses the plural grammar:

• te dane
• not ta dane

A careful pronunciation is roughly:

• dane: /ˈda.nɛ/
• są: /sɔ̃/
• ważne: /ˈvaʐ.nɛ/

Helpful notes:

• stress is on the second-to-last syllable, so DA-ne and VAŻ-ne
• ż sounds like the s in measure
• ą is a nasal vowel; in everyday speech, learners can think of it as a nasal o

A rough English-friendly approximation would be:

• DAH-ne son VAZH-ne

That is only approximate, but it is good enough as a starting point.

Yes. In other contexts, dane can also be a form meaning given, especially before another noun, for example:

• dane liczby = the given numbers

But in Dane są ważne, the natural reading is data are important.

So learners should recognize that dane can be:

• a noun meaning data
• or, in other contexts, a form meaning given

Context tells you which one it is.