Registrační značka je správná.

• registrační = an adjective modifying značka
• značka = a noun; it is the subject of the sentence
• je = is, the 3rd person singular present form of být (to be)
• správná = an adjective meaning correct/right, used as the complement after je

So the structure is basically:

[adjective + noun] + [is] + [adjective]

Because it agrees with značka, which is feminine singular.

In Czech, adjectives usually change their endings to match the noun they describe or refer to in:

• gender
• number
• case

Here, značka is feminine singular, nominative, so the predicate adjective is also feminine singular nominative:

• masculine: správný
• feminine: správná
• neuter: správné

That is why you get značka je správná.

Because registrační belongs to a different adjective pattern, often called the soft adjective pattern.

Some Czech adjectives end in -í in the dictionary form, and in nominative singular they often keep -í for all genders:

• registrační vůz
• registrační značka
• registrační číslo

So registrační is still agreeing with značka; it just does not show that agreement with an -á ending in this form.

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

Also, správná is nominative here too, because after být Czech normally uses a nominative predicate adjective:

• Značka je správná.
• Auto je nové.
• Ulice je dlouhá.

So this sentence is a straightforward nominative structure.

Because Czech does not have articles like English a/an and the.

Whether something is a registration plate or the registration plate is understood from context.

So Czech simply says:

Registrační značka je správná.

and the exact English article depends on the situation.

In a normal full sentence, je is normally required.

So the standard sentence is:

Registrační značka je správná.

If you leave out je, it may sound like:

• a note
• a headline
• a very compressed style

For a learner, it is safest to keep je in ordinary speech and writing.

Yes, Czech word order is more flexible than English word order.

The neutral, standard order here is:

Registrační značka je správná.

But other orders are possible for emphasis, for example:

Správná je registrační značka.

That sounds more marked and puts focus on správná.

So the original sentence is the most natural default version.

No. Značka has several meanings depending on context, such as:

• mark
• sign
• brand
• label

But the fixed phrase registrační značka specifically means registration plate / license plate.

So learners should understand:

• značka alone = a broader word
• registrační značka = a specific expression

Yes, it is the normal official term.

In everyday speech, you may also hear SPZ, which is very common colloquially, even though it comes from older terminology. So:

• registrační značka = official/standard
• SPZ = very common informal everyday term

That is useful because a learner may meet both.

A rough pronunciation guide is:

RE-gis-trach-nee ZNACH-ka ye SPRAAV-naa

A few helpful points:

• Czech stress is usually on the first syllable of each word.
• č sounds like ch in church
• á is a long vowel
• í is also a long vowel
• j in je sounds like English y

So:

• registrační ≈ RE-gis-trach-nee
• značka ≈ ZNACH-ka
• je ≈ ye
• správná ≈ SPRAAV-naa

Because správná means correct/right, not just good.

That distinction matters:

• správná = correct, right, valid
• dobrá = good

So if the point is that the registration plate is the correct one, správná is the right word. If you said dobrá, it would sound more like good rather than correct.