A raiva passou.

That a is the definite article, meaning the.

So a raiva literally means the anger. In Portuguese, it is very common to use the definite article with nouns in places where English might not. Here it sounds natural and complete to say A raiva passou.

If you remove the article and say Raiva passou, it sounds unusual in normal speech.

Passou is the preterite form of passar.

The verb passar has many meanings, including:

• to pass
• to go by
• to spend
• to go away
• to wear off

In this sentence, passou means something like:

• passed
• went away
• wore off
• subsided

So A raiva passou means that the feeling of anger is no longer there.

Because passar is a very natural verb in Portuguese for emotions, pain, discomfort, and temporary states that stop.

For example:

• A dor passou. = The pain went away.
• O medo passou. = The fear passed.
• A raiva passou. = The anger passed.

You could say A raiva acabou, but it may sound a little less idiomatic in some contexts.
You could also say something like A raiva foi embora, which is understandable and natural too, but passou is especially common and concise.

It is the simple past, more specifically the preterite in Portuguese.

This tense is used for something seen as completed:

• passa = passes / is passing
• passou = passed

So A raiva passou presents the anger as something that has ended.

Because the subject is a raiva, which is singular.

• a raiva = singular
• passou = third person singular

If the subject were plural, the verb would also be plural:

• As dores passaram. = The pains went away.

Not always. Raiva can mean:

• anger
• rage
• rabies

So context matters.

For example:

• Estou com raiva. = I’m angry.
• O cachorro está com raiva. can mean The dog has rabies, depending on context.

In A raiva passou, the meaning is almost certainly anger or rage, not the disease.

Yes, it is very natural.

It sounds like a normal way to say that someone’s anger has gone away. It can be used in everyday conversation, for example after an argument or a frustrating moment.

It has a calm, matter-of-fact tone.

Yes, that is a good literal translation.

But in natural English, depending on context, you might also say:

• The anger went away.
• The anger faded.
• The anger passed.
• The rage subsided.

So the literal meaning works, but English may choose slightly different wording depending on style.

Yes, depending on context.

The sentence itself does not say whose anger it is. It just says that the anger passed. In real conversation, the listener usually already knows whose anger is being discussed.

So it could be understood as:

• Her anger passed.
• His anger passed.
• The anger went away.
• She calmed down.
• He got over it.

The exact English phrasing depends on the situation.

Yes, very often.

This pattern is common with emotions, sensations, and temporary states. For example:

• O medo passou. = The fear passed.
• A tristeza passou. = The sadness passed.
• A dor passou. = The pain went away.
• O sono passou. = The sleepiness passed.

This is a very useful structure to learn.

A simple approximate pronunciation is:

ah HAI-vah pah-SOH

A few notes:

• raiva has the stress on rai
• passou has the stress on the last syllable: sou
• the final ou in Brazilian Portuguese usually sounds like oh, not like English ow

So passou sounds closer to pah-SOH than pah-SOW.

Yes. Passou and passava are different past tenses.

• passou = passed / went away
  This gives a completed event.
• passava = used to pass / was passing
  This gives an ongoing, repeated, or background idea.

So:

• A raiva passou. = The anger passed.
• A raiva passava aos poucos. = The anger was gradually going away.

For your sentence, passou is the normal choice if you mean the anger ended.