Perdemo-nos no vale.

It comes from perder-se.

• perder = to lose
• perder-se = to get lost

So in this sentence, nos is the reflexive pronoun for we/us, and perdemo-nos means we got lost or, more literally, we lost ourselves.

Because in European Portuguese, unstressed object and reflexive pronouns often come after the verb in a normal affirmative main clause. This is called enclisis.

So Portuguese writes:

perdemo-nos

not:

perdemo nos

The hyphen shows that the pronoun is cliticized to the verb.

This is a very common spelling pattern in Portuguese.

The verb form is originally perdemos. When -nos or -vos is attached to a verb form ending in -s, that final -s drops:

• perdemos + nos → perdemo-nos
• levantamos + nos → levantamo-nos

So perdemo-nos is the expected written form.

Not by form alone.

For nós, the form perdemos can be:

• present indicative: we lose
• preterite / simple past: we lost

After adding the pronoun, both become perdemo-nos. So the sentence can be ambiguous without context.

In real use, context tells you which one it is. In a narrative, it will very often mean we got lost.

In European Portuguese, not as the normal neutral version of this sentence.

A simple affirmative clause usually prefers enclisis, so:

Perdemo-nos no vale.
is the standard choice.

Nos perdemos no vale sounds more natural in Brazilian Portuguese, or it may sound marked/unusual in European Portuguese.

In European Portuguese, pronouns do come before the verb in certain environments, such as:

• Não nos perdemos.
• Quando nos perdemos...

So the position of the pronoun depends on the structure of the sentence.

No is a contraction of:

• em = in
• o = the

So:

no vale = in the valley

This kind of contraction is extremely common in Portuguese:

• em + o → no
• em + a → na
• em + os → nos
• em + as → nas

Because vale is a masculine noun: o vale.

Portuguese nouns have grammatical gender, and nouns ending in -e can be either masculine or feminine, so you often just have to learn them with the article:

• o vale = the valley
• a ponte = the bridge

That is why the sentence has no vale and not na vale.

Because Portuguese often leaves out subject pronouns when the verb form already makes the subject clear.

Here, perdemo-nos already shows first person plural: we.

So:

• Perdemo-nos no vale.
• Nós perdemo-nos no vale.

Both are possible, but the version without nós is more natural unless you want emphasis or contrast:

Nós perdemo-nos, eles não.

Yes.

• no vale = in the valley → a specific valley
• num vale = in a valley → an unspecified valley

So the article changes how specific the place is.

A rough English-style approximation is:

puhr-DEH-moo-noosh noo VAH-luh

A few useful pronunciation points:

• unstressed o often sounds like u
• final -s often sounds like sh in European Portuguese
• the final -e in vale is very weak, something like uh

So no sounds close to nu, and nos at the end sounds close to noosh.