Wolność jest ważna.

Because ważna has to agree with wolność.

In Polish, adjectives change their form to match the noun’s:

• gender
• number
• case

Wolność is a feminine singular noun, so the adjective also has to be feminine singular:

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

So:

• Wolność jest ważna. = correct

Not:

• Wolność jest ważny.
• Wolność jest ważne.

In Polish, wolność is feminine because nouns ending in -ość are typically feminine abstract nouns.

Some similar examples:

• miłość = love
• radość = joy
• młodość = youth
• wolność = freedom

So even though it does not end in -a, it is still feminine.

It is in the nominative case.

That is because wolność is the subject of the sentence:

• Wolność = freedom
• jest ważna = is important

The nominative is the basic dictionary form and is normally used for the subject.

In normal standard Polish, you usually keep jest in this kind of sentence.

So:

• Wolność jest ważna. = normal, natural sentence

Leaving it out:

• Wolność ważna.

This can sound incomplete, poetic, slogan-like, or like a headline rather than a neutral everyday sentence.

So for a learner, it is safest to use jest.

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

So Wolność jest ważna can mean:

• Freedom is important
• The freedom is important

Which meaning is intended depends on context. In this sentence, the natural reading is the general idea: Freedom is important.

The neutral word order is:

• Wolność jest ważna.

But Polish word order is fairly flexible, and changing it can change the emphasis.

For example:

• Ważna jest wolność. = emphasizes important
• Wolność jest ważna. = neutral statement

Both are grammatical, but they do not sound exactly the same in tone or focus.

A rough English-friendly approximation is:

• wolność ≈ VOL-noshch
• ważna ≈ VAZH-na

A few useful pronunciation points:

• w in Polish sounds like English v
• o is a short o
• ł would sound like English w, but there is no ł in wolność — it is a normal l
• ż sounds like the s in measure
• ść is a soft sound that English does not have exactly; shch is only an approximation

Stress is usually on the second-to-last syllable:

• WOL-ność
• WAŻ-na

It most commonly means freedom, but depending on context it can also correspond to liberty.

In many everyday sentences, freedom is the most natural English translation.
For example:

• Wolność jest ważna. = Freedom is important.

So if the meaning has already been given as freedom, that is a very natural translation.

Because after jest in this sentence, Polish uses an adjective that matches the subject.

Here, ważna describes wolność:

• freedom → important

So Polish uses the adjective form, not an adverb.

This is similar to English:

• Freedom is important.

Not:

• Freedom is importantly.

Yes, very closely:

• Wolność = freedom
• jest = is
• ważna = important

So this is one of those sentences where a word-for-word translation works quite well.

No, not in that form.

The particle to is often used in Polish for definitions or identifications, for example:

• To jest dom. = This is a house.
• Wolność to ważna wartość. = Freedom is an important value.

But in your sentence, you need:

• Wolność jest ważna.

If you use to, you would usually need a noun after it, such as:

• Wolność to podstawa. = Freedom is the foundation.
• Wolność to ważna wartość. = Freedom is an important value.

Yes. For example:

• Wolność jest istotna. = Freedom is significant / essential.
• Wolność jest cenna. = Freedom is valuable.
• Wolność jest najważniejsza. = Freedom is the most important.

But ważna is the basic, straightforward word for important, and it fits this sentence very naturally.