Převýšení je velké.

Převýšení is a noun. In this sentence, it is the subject of the sentence: the thing being described.

It is also neuter singular. That matters because the adjective velké has to match it.

A useful pattern is:

• X je Y. = X is Y.

So here:

• Převýšení = the subject
• je = is
• velké = large / great / big

Because Czech adjectives must agree with the noun they describe in gender, number, and case.

Převýšení is:

• neuter
• singular
• nominative

So the adjective must also be:

• neuter
• singular
• nominative

That gives velké.

Compare:

• hrad je velký = the castle is big (masculine)
• hora je velká = the mountain is big (feminine)
• převýšení je velké = the elevation gain is big (neuter)

Je is the 3rd person singular present tense of být = to be.

So:

• je = is

The sentence structure is completely normal:

• Převýšení je velké.
• literally: The elevation gain is large.

English also uses is, so this part matches English quite closely.

Usually, no.

In Czech, subject pronouns are often omitted, but the verb itself normally stays:

• Je velké. = It is large.
• Převýšení je velké. = The elevation gain is large.

You would not normally say just:

• Převýšení velké.

That sounds incomplete in standard Czech.

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

The adjective velké is also in the nominative, because after být (to be), Czech normally uses a predicate adjective in nominative form.

So both main words are nominative singular neuter here.

Not completely. Czech word order is fairly flexible, but the neutral order here is:

• Převýšení je velké.

You could also hear:

• Velké je převýšení.

But that sounds more marked or stylistic, with extra emphasis on velké.

For a learner, the basic pattern subject + je + adjective is the safest and most natural choice.

A rough pronunciation guide is:

• pře-vý-še-ní

Some important points:

• ř is the famous Czech sound that is hard for English speakers. It is somewhat like a rolled r mixed with a zh/sh quality.
• ý is a long vowel, so say it longer than a short i/y sound.
• š sounds like English sh.
• ní has a long í, so the last syllable is also long.

You do not need to master ř immediately. Even if your ř sounds closer to r or zh, people will usually still understand you.

In this word, yes: převýšení is a neuter noun.

Many Czech nouns ending in -í are neuter, especially nouns formed from verbs, often describing an action, process, or result.

So a learner can often treat this type as a clue:

• -í often suggests a neuter noun

But do not rely on endings alone in every case. It is a helpful pattern, not a perfect rule for all nouns.

All of those can work depending on context.

Velký / velká / velké is a very common adjective meaning:

• big
• large
• sometimes great or considerable

In this sentence, the most natural English choice depends on the context you were given. For something like elevation gain, English often prefers:

• large
• great
• significant in some contexts

But grammatically, velké is just the ordinary adjective meaning big/large.

Yes, veliké is possible. It means something like very large / great / big, but it can sound a bit more literary, expressive, or emphatic than velké.

In everyday neutral Czech, velké is the safest choice.

So:

• Převýšení je velké. = neutral, standard
• Převýšení je veliké. = also correct, but a bit stronger or more expressive

Yes, grammatically it can have a plural, but whether that sounds natural depends on context.

Singular:

• převýšení je velké = the elevation gain is large

Plural could be used when talking about several climbs, routes, or sections:

• Převýšení jsou velká. = the elevation gains are large

Notice that in the plural, the adjective changes too:

• singular neuter: velké
• plural neuter: velká

That change is normal Czech adjective agreement.