A cadela começa a abanar o rabo quando a Ana chega a casa.

Yes. Cadela is specifically female dog.

• o cão = the dog / male dog
• a cadela = the female dog

In everyday use, cão can also sometimes be used more generally for dog, but cadela clearly tells you the animal is female.

Because a is the feminine singular definite article, meaning the.

• a cadela = the female dog

It matches the gender and number of the noun:

• o cão = the dog
• a cadela = the female dog
• os cães = the dogs
• as cadelas = the female dogs

It means starts wagging or more literally begins to shake/move.

Breakdown:

• começa = starts / begins
• a abanar = to wag / to shake

In Portuguese, after começar, it is very common to use a + infinitive:

• começar a falar = to start speaking
• começar a correr = to start running
• começar a abanar = to start wagging

So A cadela começa a abanar o rabo = The female dog starts wagging its tail.

Because in Portuguese, the normal structure after começar is começar a + infinitive.

So:

• começa a abanar = starts wagging

This is the standard and natural pattern in European Portuguese.

English often uses start + -ing, but Portuguese usually uses:

• começar a + infinitive

Examples:

• Ela começa a rir. = She starts laughing.
• Eles começam a trabalhar. = They start working.

Here abanar means to wag.

Its basic meaning is to shake, to wave, or to move back and forth. With tail, it naturally becomes wag in English.

Examples:

• abanar a cabeça = to shake one’s head
• abanar a mão = to wave one’s hand
• abanar o rabo = to wag the tail

So the exact English translation depends on what is being moved.

Because Portuguese often uses the definite article with body parts instead of a possessive.

So Portuguese prefers:

• abanar o rabo = wag the tail

rather than:

• abanar o seu rabo

In English, we usually say its tail, but in Portuguese the ownership is often understood from the context.

This is very common with body parts:

• Lavou as mãos. = He/She washed his/her hands.
• Fechou os olhos. = He/She closed his/her eyes.

In this sentence, yes: rabo means tail.

But be aware that rabo can also mean bottom / backside in some contexts, so it can sound a bit informal or humorous depending on how it is used.

For animals, though, o rabo is very normal and natural.

A more formal or technical word is:

• cauda = tail

But for a dog, abanar o rabo is exactly the kind of phrase native speakers commonly say.

Because in European Portuguese, it is very common to use the definite article before a person’s name.

So:

• a Ana = Ana
• o João = João

This does not change the meaning into the Ana in English. It is just a normal feature of Portuguese.

Examples:

• A Ana chegou. = Ana arrived.
• O Pedro está em casa. = Pedro is at home.

This is especially common in Portugal. Learners often notice it because English does not do this.

Because they are doing different jobs.

• quando = when
• a = the article used before the name Ana
• Ana = Ana

So quando a Ana chega simply means when Ana arrives.

The second a is not part of quando. It belongs to Ana.

Chega is the present tense of chegar = to arrive.

Here the present tense is used to describe something that happens regularly or typically:

• A cadela começa a abanar o rabo quando a Ana chega a casa.

This suggests a repeated situation:

• Whenever Ana gets home, the dog starts wagging its tail.

Portuguese, like English, often uses the present tense for habits and repeated actions.

It means arrives home or gets home.

Breakdown:

• chega = arrives
• a casa = home

So:

• chegar a casa = to arrive home / to get home

This is a very common expression in European Portuguese.

Because casa here means home in a general, idiomatic sense, and Portuguese commonly says:

• ir a casa = to go home
• chegar a casa = to get home
• voltar a casa = to return home

There is no article here, so there is no contraction into à.

Compare:

• A Ana chega a casa. = Ana gets home.
• A Ana chega à casa da mãe. = Ana arrives at her mother’s house.

In the second sentence, à appears because it is a + a casa:

• preposition a
• article a

So a casa = home
but à casa da Ana = to Ana’s house / at Ana’s house

It is especially characteristic of European Portuguese usage.

In Portugal, chegar a casa is the normal form.

Learners may also hear forms like chegar em casa in Brazilian Portuguese, but for European Portuguese, chegar a casa is the form you should learn and use.

It has two parts:

1. A cadela começa a abanar o rabo
   = The female dog starts wagging its tail

2. quando a Ana chega a casa
   = when Ana gets home

So the full structure is:

• main clause: A cadela começa a abanar o rabo
• time clause introduced by quando: quando a Ana chega a casa

A literal breakdown is:

• A cadela = the female dog
• começa = starts
• a abanar = to wag
• o rabo = the tail
• quando = when
• a Ana = Ana
• chega = arrives
• a casa = home

Yes, absolutely.

That version is also correct:

• Quando a Ana chega a casa, a cadela começa a abanar o rabo.

It means the same thing. The only difference is emphasis and sentence flow.

• Starting with A cadela... puts the focus first on the dog.
• Starting with Quando a Ana chega a casa... puts the time situation first.

Both are natural.

Most naturally, it describes a habitual/repeated action:

• Whenever Ana gets home, the dog starts wagging its tail.

The present tense in both clauses strongly suggests this kind of regular event.

If you wanted to describe one specific past event, Portuguese would normally use past forms instead, for example:

• A cadela começou a abanar o rabo quando a Ana chegou a casa.
• The dog started wagging its tail when Ana got home.

Yes, depending on context.

In this sentence, because the verbs are in the present tense and the meaning is habitual, quando is naturally understood as something like:

• when
• whenever

So the sentence can be understood as:

• The dog starts wagging its tail when Ana gets home.
• The dog starts wagging its tail whenever Ana gets home.

English may choose either wording depending on style, but the Portuguese sentence itself is perfectly natural as it is.