Grzbiet jest wysoki, a zbocze strome.

Yes, Grzbiet jest wysoki, a zbocze jest strome is fully correct.

In your sentence, the second jest is simply left out because it is understood from the first clause. This is a very common kind of ellipsis in Polish, especially when two parallel descriptions are joined together.

So these mean the same thing:

• Grzbiet jest wysoki, a zbocze strome.
• Grzbiet jest wysoki, a zbocze jest strome.

The version without the second jest sounds a bit more concise and stylistically neat.

Here a means something like and, but more specifically and/while, often with a slight contrast.

So a is often used when you are:

• comparing two things,
• setting them side by side,
• or showing a mild contrast.

In this sentence, it links two parallel descriptions:

• the ridge is high
• the slope is steep

It is not as neutral as i, which is the basic and.

Compare:

• Jan jest wysoki i silny. = Jan is tall and strong.

  • simple addition

• Jan jest wysoki, a Piotr niski. = Jan is tall, while Piotr is short.

  • contrast / comparison

In your sentence, a works well because the two landscape features are being described separately, side by side.

Because in Polish, a is normally preceded by a comma when it joins two clauses.

So:

• Grzbiet jest wysoki, a zbocze strome.

This is standard Polish punctuation.

You will often see the same with:

• ale = but
• więc = so
• lecz = however/but

By contrast, i often does not take a comma when it simply joins words or clauses in a straightforward way.

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

Here:

• grzbiet is masculine singular
• zbocze is neuter singular

So the adjectives change to match:

• wysoki → masculine singular
• strome → neuter singular

A very simplified pattern is:

• masculine: wysoki
• feminine: wysoka
• neuter: wysokie

and similarly:

• masculine: stromy
• feminine: stroma
• neuter: strome

So:

• grzbiet jest wysoki
• zbocze jest strome

• grzbiet is masculine
• zbocze is neuter

You can often recognize neuter nouns because many of them end in -e or -o, and zbocze follows that pattern.

Knowing the gender is important because it affects:

• adjective endings,
• past tense verb forms,
• pronouns,
• and some numeral forms.

That is exactly why the sentence has:

• wysoki with grzbiet
• strome with zbocze

They are in the nominative.

That is because:

• grzbiet and zbocze are the subjects of their clauses,
• and with być
  • adjective, Polish normally uses the adjective in the nominative too.

So:

• grzbiet → nominative singular
• wysoki → nominative singular masculine
• zbocze → nominative singular
• strome → nominative singular neuter

This is different from some noun complements after być, where Polish often uses the instrumental:

• On jest nauczycielem. = He is a teacher.

But with adjectives:

• On jest wysoki. = He is tall.

You might see something like that in:

• poetic language,
• headlines,
• captions,
• notes,
• or very compressed style.

But in normal standard sentence-building, Grzbiet jest wysoki, a zbocze strome is much safer and more natural.

So for a learner, the best rule is:

• keep jest in the first clause,
• and understand that it may be omitted in the second if the structure is parallel.

Because Polish has no articles.

So Polish nouns do not have separate words for:

• a/an
• the

That means grzbiet can mean:

• a ridge
• the ridge

and zbocze can mean:

• a slope
• the slope

The exact meaning depends on context.

This is very normal in Polish, and English speakers often notice it quickly because English requires articles much more often.

The given word order is natural and clear, but Polish word order is more flexible than English.

The basic version:

• Grzbiet jest wysoki, a zbocze strome.

is neutral and straightforward.

You can sometimes rearrange words for emphasis, for example:

• Wysoki jest grzbiet, a strome zbocze.

But that sounds more marked, literary, or contrastive.

For everyday learning, the original order is best:

• subject + jest + adjective

A rough guide:

• grzbiet ≈ gzh-byet
• zbocze ≈ zbo-che

A few useful details:

• rz usually sounds like the zh in measure
• cz sounds like ch in chop
• ie often gives a ye-like sound after a consonant

So:

• grzbiet ≈ gzh-byet
• wysoki ≈ vih-SO-kee
• zbocze ≈ ZBO-che
• strome ≈ STRO-me

The stress in Polish is usually on the second-to-last syllable:

• wy-SO-ki
• ZBO-cze
• STRO-me

Yes, both are normal words, especially in geography, hiking, and descriptions of terrain.

• grzbiet can mean ridge, especially a mountain ridge
• zbocze means slope, hillside, or the side of a hill/mountain

A useful thing to know is that grzbiet can also mean back or spine/ridge in other contexts, depending on the object being described. Polish often uses the same word for a raised, back-like shape.

So in a landscape sentence, grzbiet is best understood as ridge.

Grammatically, you might sometimes see i, but a is better here.

Why?

Because the sentence has a paired, descriptive structure:

• one feature is described,
• then another feature is described.

Polish often prefers a in this kind of side-by-side comparison:

• Grzbiet jest wysoki, a zbocze strome.

Using i would sound more like simple addition:

• The ridge is high and the slope is steep

That is not impossible in meaning, but a is the more natural choice for this balanced structure.

Yes. It sounds concise, descriptive, and natural, especially in written or formal description.

A fuller version:

• Grzbiet jest wysoki, a zbocze jest strome.

is also completely natural.

The shorter version with the omitted second jest is especially nice when the two halves are parallel, as they are here.