Os caminhantes voltaram com as botas de caminhada molhadas.

Os is the masculine plural definite article, meaning the.

• o = the (masculine singular)
• os = the (masculine plural)
• a = the (feminine singular)
• as = the (feminine plural)

Here, caminhantes is a plural noun, and it is treated as masculine in this sentence, so Portuguese uses os caminhantes = the walkers / the hikers.

Unlike English, Portuguese usually uses articles much more regularly before nouns.

Caminhantes means walkers or hikers, depending on context.

It comes from the verb caminhar, which means to walk or to hike.

So:

• caminhar = to walk / to hike
• caminhante = walker / hiker
• caminhantes = walkers / hikers

In this sentence, because of botas de caminhada (hiking boots), hikers is probably the most natural interpretation.

Voltaram is the pretérito perfeito (simple past / preterite) of the verb voltar.

• voltar = to return / to come back
• voltaram = they returned / they came back

It is the 3rd person plural form, used for they.

For an -ar verb like voltar, the preterite endings are:

• eu voltei
• tu voltaste
• ele/ela/você voltou
• nós voltámos (European Portuguese spelling with accent)
• vós voltastes
• eles/elas/vocês voltaram

So Os caminhantes voltaram = The hikers returned / came back.

Com means with.

In this sentence, it links the hikers to something they had when they returned:

• voltaram com as botas... = they returned with the boots...

So the idea is that when they came back, their hiking boots were wet.

This does not mean they returned together with the boots as separate objects in the way English might sometimes imply. It simply describes their condition or what they had on them when they returned.

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

So:

• botas de caminhada = literally boots of walking/hiking
• natural English: hiking boots

This structure is very common in Portuguese:

• sapatos de corrida = running shoes
• roupa de inverno = winter clothes
• mesa de jantar = dining table

So de caminhada describes the type or purpose of the boots.

Yes, in meaning it is very close.

• botas de caminhada = hiking boots / walking boots
• literally: boots of walking/hiking
• naturally: boots for walking/hiking

Portuguese often prefers de in set expressions like this, even where English might prefer for or just a noun used adjectivally.

You could sometimes hear botas para caminhar, but botas de caminhada is the more idiomatic label for the type of boot.

Because it agrees with botas, which is a feminine plural noun.

• bota = boot
• botas = boots
• molhado = wet (masculine singular)
• molhada = wet (feminine singular)
• molhados = wet (masculine plural)
• molhadas = wet (feminine plural)

So:

• as botas molhadas = the wet boots

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

It describes the boots, not the hikers.

You can tell because molhadas is feminine plural, matching botas.

If the sentence meant that the hikers were wet, you would expect molhados, because caminhantes here is masculine plural:

• Os caminhantes voltaram molhados. = The hikers came back wet.
• Os caminhantes voltaram com as botas de caminhada molhadas. = The hikers came back with their hiking boots wet.

So the grammar makes the reference clear.

In Portuguese, adjectives often come after the noun.

So:

• as botas de caminhada molhadas

literally follows the pattern:

• the boots of hiking wet

This sounds strange in English, but it is normal in Portuguese.

Placing molhadas at the end is natural because it modifies the whole noun phrase as botas de caminhada.

Yes, but some versions sound more natural than others.

The original sentence is very natural:

• Os caminhantes voltaram com as botas de caminhada molhadas.

You could also say:

• Os caminhantes voltaram com as botas molhadas.
  if the de caminhada part is unnecessary from context

• Com as botas de caminhada molhadas, os caminhantes voltaram.
  more literary or stylistically marked

But changing the position of molhadas inside the phrase can sound awkward:

• as molhadas botas de caminhada → very unnatural in normal speech
• as botas molhadas de caminhada → sounds odd, because de caminhada normally stays close to botas

So the original order is the most straightforward one.

Both are correct.

• returned is slightly more formal or neutral
• came back is often more conversational

So:

• Os caminhantes voltaram = The hikers returned
• Os caminhantes voltaram = The hikers came back

Which one sounds better depends on the style of the English translation, not on any difference in the Portuguese sentence.

A broad European Portuguese pronunciation would be approximately:

Oosh cami-NHAN-tesh vohl-TA-rãw cõm ash BO-tash d’ cami-NHA-dɐ moo-LYA-dash

A few useful pronunciation points:

• os before a consonant often sounds like oosh in European Portuguese
• nh in caminhantes / caminhada sounds like ny in canyon
• lh in molhadas sounds like lli in million, but smoother
• unstressed final a is often reduced in European Portuguese, so caminhada does not end with a strong English-style ah

The exact pronunciation varies by region, but these are the main features learners usually need to notice.