O cachorro tentou fugir.

O is the masculine singular definite article, equivalent to the in English.

• o cachorro = the dog
• um cachorro = a dog

Because the sentence is talking about the dog, Portuguese uses o.

The noun cachorro is masculine here.

• o cachorro = the male dog / the dog
• a cachorra = the female dog

In everyday Portuguese, cachorro can also be used generically for dog, even when the sex is not important. If you specifically want to say the dog is female, you would say a cachorra.

Yes, both cachorro and cão can mean dog, but cachorro is much more common in everyday Brazilian Portuguese.

A few notes:

• cachorro = the normal everyday word for dog
• cão = also means dog, but sounds more formal, literary, or fixed in expressions

So in normal conversation, O cachorro tentou fugir sounds very natural.

Tentou is the 3rd person singular preterite form of tentar.

That means:

• tentar = to try
• tentou = tried

It matches the subject o cachorro because the dog is he/she/it in grammar terms.

Why not the others?

• tentar is the infinitive: to try
• tentava is the imperfect: was trying / used to try / would try
• tentou gives a completed past action: tried

So O cachorro tentou fugir means the dog made an attempt to escape.

After tentar, Portuguese normally uses another verb in the infinitive.

So:

• tentou fugir = tried to escape
• literally: tried escape

This is very common in Portuguese:

• começou a chover = it started to rain
• quer sair = wants to leave
• precisa estudar = needs to study

With tentar, you usually just use the infinitive directly, without a preposition:

• tentar fugir
• tentar abrir
• tentar entender

Because Portuguese and English structure this differently.

In English, you say:

• tried to escape

In Portuguese, after tentar, you normally say:

• tentou fugir

There is no separate word corresponding to English to here. The infinitive fugir already does that job in Portuguese grammar.

A rough pronunciation guide is:

• O cachorro ≈ u ka-SHO-hu
• tentou ≈ ten-TOH
• fugir ≈ foo-ZHEER

A few key sounds:

• ch in cachorro sounds like sh
• rr in cachorro is usually a strong throaty h sound in Brazilian Portuguese
• final o often sounds like u
• gi in fugir sounds like zhi or jhi, similar to the s in measure

So the whole sentence is roughly:

u ka-SHO-hu ten-TOH foo-ZHEER

Portuguese often does not need an explicit subject pronoun when the subject is already stated.

Here, o cachorro is the subject, so adding ele would be unnecessary.

• O cachorro tentou fugir. = natural
• Ele tentou fugir. = He tried to escape.
  This works only if it is already clear that ele refers to the dog.

Portuguese often prefers the noun itself or simply leaves the pronoun out when the meaning is clear.

It is in the preterite past tense, specifically with tentou.

The preterite is used for a finished action in the past.

• O cachorro tentou fugir. = The dog tried to escape.
  This presents the attempt as a completed event.

Compare:

• O cachorro tentava fugir. = The dog was trying to escape / used to try to escape.

So tentou focuses on one completed attempt.

Yes. Fugir and escapar are both possible, and both can mean to escape.

Very roughly:

• fugir often emphasizes running away / fleeing
• escapar often emphasizes getting away / escaping

In many everyday contexts, they overlap a lot. So:

• O cachorro tentou fugir.
• O cachorro tentou escapar.

Both are natural.

The normal and most natural order is:

• O cachorro = subject
• tentou = verb
• fugir = infinitive complement

So:

• O cachorro tentou fugir.

Portuguese does allow some flexibility in word order, but unusual orders can sound literary, marked, or unnatural in ordinary speech. For a learner, this standard order is the best one to use.

You would make both the article/noun and the verb plural where needed:

• Os cachorros tentaram fugir. = The dogs tried to escape.

Changes:

• o → os
• cachorro → cachorros
• tentou → tentaram

The infinitive fugir stays the same.

For a negative sentence, put não before the verb:

• O cachorro não tentou fugir. = The dog didn’t try to escape.

For a yes/no question, Brazilian Portuguese often keeps the same word order and uses intonation:

• O cachorro tentou fugir? = Did the dog try to escape?

In writing, the question mark shows it clearly. In speech, your voice rising at the end helps mark it as a question.