El rascacielos es muy alto.

Rascacielos is a compound noun (from rasca + cielos) that ends in -s but is grammatically singular here. Spanish has a few nouns like this.

• el rascacielos = the skyscraper (singular)
• los rascacielos = the skyscrapers (plural — the word itself does not change)

So the -s at the end does not automatically mean plural; the article (el / los) tells you whether it is singular or plural in this case.

You do not change the noun itself; only the article changes:

• Singular: el rascacielos es muy alto – the skyscraper is very tall
• Plural: los rascacielos son muy altos – the skyscrapers are very tall

Notice:

• el → los
• es → son
• alto → altos

But rascacielos stays the same.

Both ser (es) and estar (está) can be used with adjectives, but they mean different things:

• es muy alto uses ser to describe an essential, permanent characteristic of the building: its height.
• está muy alto with a building would usually sound odd if you mean tall.

Está muy alto is more natural for:

• physical position:
  
  • El avión está muy alto. – The plane is (flying) very high.
• temporary or changeable states:
  
  • El precio está muy alto. – The price is very high right now.

For the inherent height of a skyscraper, you normally say es muy alto.

Adjectives agree with the grammatical gender and number, not with how the word looks.

• rascacielos here is masculine singular, so the adjective must also be masculine singular: alto.
• If it were plural: los rascacielos son muy altos (masculine plural adjective).

The final -s in rascacielos is just part of the word, not a plural ending.

Yes, but the meaning changes.

• El rascacielos es muy alto.
  You are describing how tall the building is (its height).

• El rascacielos está muy alto.
  This would normally be interpreted as about its position or level, for example:

  • Maybe you are looking from far away and saying it is located very high up on a hill/cliff.
  • Or in some figurative contexts (like prices, positions in rankings), though with buildings this is less common.

For ordinary descriptions of a building’s height, you say es muy alto.

Muy and mucho are used differently:

• muy goes before adjectives and adverbs:

  • muy alto – very tall
  • muy rápido – very fast
  • muy bien – very well

• mucho usually goes with verbs or nouns:

  • trabaja mucho – he/she works a lot
  • tiene mucho dinero – he/she has a lot of money

So:

• ✅ es muy alto
• ❌ es mucho alto (incorrect in standard Spanish)

There are two different structures:

1. Predicate adjective (after the verb):

   • El rascacielos es muy alto.
     You are making a statement about the skyscraper. This is the normal way to say The skyscraper is very tall.

2. Attributive adjective (next to the noun):

   • el rascacielos alto
     This could work in context, but it is more like the tall skyscraper (as opposed to some other skyscraper). It identifies or distinguishes rather than simply describes.

So:

• To just describe: El rascacielos es muy alto.
• To distinguish one from others: El rascacielos alto está en el centro. – The tall skyscraper is downtown.

You can, but it sounds different and less neutral.

• El rascacielos es muy alto.
  Simple, neutral description: The skyscraper is very tall.

• El muy alto rascacielos
  This is more literary or emphatic, like the very tall skyscraper. It sounds a bit more stylistic, like something you might see in writing rather than everyday speech.

In everyday conversation, the standard is El rascacielos es muy alto.

Yes. It is a compound word:

• rasca – from the verb rascar, to scratch
• cielos – skies

So rascacielos = sky-scratcher, which matches the English skyscraper.

Even though cielos is plural inside the word, the whole compound rascacielos is treated as a single noun: singular or plural is determined by the article (el / los) and verb (es / son).

Rascacielos is widely understood and used throughout the Spanish-speaking world, including Latin America.

In many Latin American countries, you will hear:

• rascacielos – skyscraper
• edificio alto / edificio muy alto – tall building / very tall building

In everyday speech people might say edificio alto more often, but rascacielos is standard, correct, and common in media, writing, and educated speech across Latin America.

No, you generally cannot drop the article here.

Spanish usually needs a definite article with singular countable nouns when you are talking about a specific one:

• ✅ El rascacielos es muy alto.
• ❌ Rascacielos es muy alto. (sounds wrong unless Rascacielos is a proper name of something, like a ship or movie)

For generic statements about a class:

• Los rascacielos son muy altos. – Skyscrapers are very tall.
  (The definite article los is still used in generic statements.)

Rascacielos has four syllables:
ras–ca–cie–los

Pronunciation tips:

• ras – like rahs (short a, as in Spanish casa)
• ca – kah
• cie – in Latin American Spanish, cie sounds like syeh (because ci = see, but with a y glide before e)
• los – lohs

Stress falls on cie: ras-ca-CIE-los

There is no written accent mark because words ending in -s are normally stressed on the second-to-last syllable, and rascacielos follows that rule.

Yes, there is a nuance:

• muy alto – very tall
  Neutral, common, just says the skyscraper is very tall.

• altísimo – extremely tall / super tall
  More emphatic, expressive. It sounds stronger, a bit more dramatic:

  • El rascacielos es altísimo.

You can use either, depending on how strong you want your statement to be. In everyday speech, muy alto is very frequent; altísimo adds emphasis.

The gender of rascacielos is masculine by convention, so it takes el:

• el rascacielos
• un rascacielos
• los rascacielos

There is no obvious ending (like -o or -a) to signal gender; many compound nouns behave this way, and you have to learn their gender with the word.

A practical tip:

• When you learn a noun that is not obviously masculine or feminine, always learn it together with its article:
  
  • el rascacielos, el sofá, la mano, etc.