Národní plán je důležitý.

A good English-style approximation is NAA-rod-nee plaan ye DOO-le-zhi-tee.

A few key points:

• Stress is on the first syllable of each word: NÁ-rodní, PLÁN, JE, DŮ-le-ži-tý
• á, í, ů, ý are long vowels
• ž sounds like the s in measure

So the sentence sounds roughly like: NAA-rod-nee plaan ye DOO-le-zhi-tee.

Czech does not use articles.

So Národní plán je důležitý can mean:

• The national plan is important
• A national plan is important

The exact meaning depends on context.

Národní is an adjective meaning national.

Here it comes before the noun plán and directly describes it, so národní plán means national plan as one noun phrase.

Compare:

• národní plán = national plan
• Plán je národní = The plan is national

Those are related, but not the same structure.

Because národní belongs to a type of adjective that has -í in the nominative singular for all genders.

So you can say:

• národní plán — masculine
• národní strategie — feminine
• národní muzeum — neuter

So the form národní does not change here just because the noun changes gender.

Plán is a masculine inanimate noun.

That matters because Czech adjectives must agree with the noun in gender and number. So when the sentence says the plan is important, the adjective has to match plán.

That is why the sentence has:

• důležitý for masculine singular

Důležitý is the adjective important, and here it is a predicate adjective: it describes the subject after je (is).

In Czech, this adjective agrees with the subject:

• masculine singular: důležitý
• feminine singular: důležitá
• neuter singular: důležité

Since plán is masculine singular, důležitý is the correct form.

Národní plán is in the nominative singular because it is the subject of the sentence.

Důležitý is also nominative singular, because with být (to be), Czech normally uses a nominative adjective to describe the subject.

So this is a very standard pattern:

• subject in nominative
• form of být
• adjective agreeing with the subject

Je means is. It is the 3rd person singular form of být (to be).

In normal Czech, you usually must keep it. Czech often drops subject pronouns, but it does not normally drop je in an ordinary sentence like this.

So:

• Národní plán je důležitý. = correct
• Národní plán důležitý. = normally incomplete

Yes, Czech word order is more flexible than English, but Národní plán je důležitý is the most neutral and basic version.

For example:

• Národní plán je důležitý. — neutral statement
• Důležitý je národní plán. — emphasizes important or contrasts it with something else

So learners should treat the original sentence as the default word order.

The adjective after je changes to match the new subject.

For example:

• Národní strategie je důležitá. — feminine
• Národní opatření je důležité. — neuter
• Národní plány jsou důležité. — plural

This is a very useful pattern to learn, because Czech uses it constantly.