Hoje meu filho vestiu o uniforme cedo porque a aula começa às oito.

Because vestir can be used in two common ways:

• vestir + clothing item = to put on / wear something
  
  • vestiu o uniforme = he put on the uniform
• vestir-se = to get dressed

So in this sentence, vestiu o uniforme is natural because the clothing item is named directly. If you said Hoje meu filho se vestiu cedo, that would mean Today my son got dressed early, without focusing on what he put on.

Because começa às oito describes a schedule or fixed fact: class starts at eight.

Portuguese often uses the present tense for:

• schedules
• routines
• timetables
• general facts

So the sentence mixes:

• vestiu = a completed action in the past
• começa = a present-tense statement about when the class starts

This is very natural in both Portuguese and English:

• He got dressed early because class starts at eight.

Às oito means at eight or at eight o’clock.

The form às is a contraction of:

• a = at / to
• as = the feminine plural article

So:

• a + as = às

This contraction is very common before clock times:

• à uma = at one
• às duas = at two
• às oito = at eight

You can also say às oito horas, but às oito is enough in normal speech.

Portuguese uses definite articles more often than English.

Here, a aula means the class—the specific class relevant in the situation, probably the child’s class that day.

In English, we might say:

• because class starts at eight

But in Portuguese, it is very natural to include the article:

• porque a aula começa às oito

In Brazilian Portuguese, both forms can exist:

• meu filho
• o meu filho

The version without the article is completely natural, especially in many neutral or straightforward sentences.

With family words like:

• meu pai
• minha mãe
• meu filho

the article may appear or be omitted depending on region, style, and speaker preference.

So:

• Hoje meu filho vestiu o uniforme cedo...
• Hoje o meu filho vestiu o uniforme cedo...

Both are possible, but the version in your sentence sounds perfectly normal.

That’s exactly right: nouns ending in -e can be masculine or feminine, so you usually have to learn their gender individually.

Here:

• o uniforme = masculine

So you say:

• o uniforme novo
• um uniforme
• meu uniforme

There is no reliable rule that all -e nouns have the same gender, so this one simply has to be memorized.

Here, cedo is an adverb, meaning early.

It modifies the verb:

• vestiu cedo = got dressed / put on the uniform early

As an adverb, cedo does not change form.

Examples:

• Ele chegou cedo. = He arrived early.
• Ela acordou cedo. = She woke up early.

Yes. Portuguese word order is flexible, and this sentence could be rearranged in several natural ways depending on emphasis.

The original:

• Hoje meu filho vestiu o uniforme cedo porque a aula começa às oito.

Other possible versions:

• Meu filho vestiu o uniforme cedo hoje porque a aula começa às oito.
• Porque a aula começa às oito, hoje meu filho vestiu o uniforme cedo.
• Hoje, porque a aula começa às oito, meu filho vestiu o uniforme cedo.

The original version is natural because:

• Hoje sets the time frame right away
• cedo comes near the verb phrase it modifies
• porque... gives the reason at the end

In this sentence, porque means because.

This is one of several similar-looking forms in Portuguese:

• porque = because
  
  • Ele saiu cedo porque estava cansado.
• por que = why / for what reason
  
  • Por que ele saiu cedo?
• porquê = the reason, the why
  
  • Não entendi o porquê.
• por quê = used at the end of a question
  
  • Ele saiu cedo por quê?

So here, porque is correct because the sentence is giving a reason.

It can mean either, depending on context.

In this sentence, a aula começa às oito most naturally means:

• class starts at eight or
• the lesson starts at eight

In everyday Brazilian Portuguese, aula is used very often for:

• a school class
• a lesson
• a period of instruction

So the exact English translation depends on context, but the Portuguese word is the normal one in either case.