O abrigo de montanha está vazio.

Because o is the definite article, meaning the.

So:

• o abrigo = the shelter
• abrigo = shelter / a shelter in a more general or dictionary-like sense

In Portuguese, articles are used very often, more often than in English. In a normal sentence, O abrigo de montanha está vazio sounds natural as The mountain shelter is empty.

If you said just Abrigo de montanha está vazio, it would usually sound incomplete unless it appeared in a special context such as a headline, sign, or note.

Here, abrigo means shelter, refuge, or hut, depending on context.

In abrigo de montanha, it refers to a shelter in the mountains, often used by hikers or climbers. In English, possible translations include:

• mountain shelter
• mountain refuge
• mountain hut

The basic word abrigo can also mean shelter in a broader sense, such as protection from weather.

Portuguese often uses de + noun where English uses a noun as an adjective.

So:

• abrigo de montanha = literally shelter of mountain
• natural English: mountain shelter

This structure is extremely common in Portuguese:

• casa de campo = country house
• saco de plástico = plastic bag
• óculos de sol = sunglasses

So de montanha is the normal way to say mountain as a type/category here.

This is a very common question, because Portuguese has two verbs for to be: ser and estar.

Here, está vazio is used because being empty is understood as a state or condition, not a permanent defining characteristic.

• está vazio = is empty right now / at this moment / in this situation

Examples:

• O abrigo está vazio. = The shelter is empty.
• A garrafa está vazia. = The bottle is empty.

Using ser here would sound unusual in most normal contexts, because emptiness is usually temporary.

Because it agrees with abrigo, which is a masculine singular noun.

In Portuguese, adjectives usually agree in gender and number with the noun they describe.

• o abrigo = masculine singular
• therefore: vazio = masculine singular

Compare:

• o abrigo está vazio = the shelter is empty
• a cabana está vazia = the cabin is empty
• os abrigos estão vazios = the shelters are empty
• as cabanas estão vazias = the cabins are empty

One clue is the article: o abrigo.

You usually learn the gender of a noun together with its article:

• o abrigo = masculine
• a montanha = feminine

It is true that many nouns ending in -o are masculine, but that is only a tendency, not a perfect rule. The safest habit is to memorize nouns with their article.

Because the normal Portuguese word order is:

subject + verb + adjective/complement

So:

• O abrigo = subject
• está = verb
• vazio = adjective/complement

That gives:

O abrigo está vazio.

You might see a different order in poetry, dramatic writing, or for emphasis, but for everyday Portuguese this standard order is the natural one.

Yes, but it does not mean exactly the same thing.

• abrigo de montanha usually means a mountain shelter as a type of shelter
• abrigo da montanha means the shelter of the mountain or the shelter on/from the mountain, depending on context

So de montanha is the normal expression when you mean a shelter intended for mountain use or located in the mountains as a category.

In European Portuguese, está is commonly pronounced roughly like shtah, not like a fully clear es-TAH as an English speaker might expect.

A helpful approximation is:

• está ≈ shtah

This happens because in European Portuguese, unstressed e often becomes very reduced or almost disappears, and s before another consonant often sounds like sh.

So the whole sentence in European Portuguese may sound more compressed than you expect.

A rough learner-friendly approximation is:

u uh-BREE-go d' مون-TA-nya shta va-ZEE-u

A slightly more careful breakdown:

• O → often sounds close to u
• abrigo → uh-BREE-go
• de → often reduced, something like d(uh) or just d
• montanha → mon-TA-nya
• está → shta
• vazio → va-ZEE-u

A key point: European Portuguese often reduces unstressed vowels, so words run together more than in English or in many learners’ expectations.

Not necessarily. In abrigo de montanha, the singular montanha is part of a fixed type expression, like mountain shelter.

It describes the kind of shelter, not the number of mountains nearby.

So even if the shelter is in a mountain range, Portuguese still normally says:

• abrigo de montanha

This is similar to how English says mountain shelter, not usually mountains shelter.

Yes. That is a good translation.

Depending on context, abrigo de montanha can be translated as:

• mountain shelter
• mountain refuge
• mountain hut

The best choice depends on what kind of building it is and how natural you want the English to sound in context.

The plural would be:

Os abrigos de montanha estão vazios.

Changes:

• o → os
• abrigo → abrigos
• está → estão
• vazio → vazios

Notice that de montanha does not change here, because montanha is part of the expression and is not the noun being counted.