Hoje eu estou sem sono, então vou estudar português.

Yes. In Brazilian Portuguese, subject pronouns are often optional, especially when the verb form already makes the subject clear.

So both of these are natural:

• Hoje eu estou sem sono, então vou estudar português.
• Hoje estou sem sono, então vou estudar português.

Including eu can add a little emphasis or simply make the sentence feel clearer in conversation. In everyday Brazilian Portuguese, people often use subject pronouns more than in some other varieties of Portuguese, but leaving eu out is still very common.

Because estar is used for a temporary state or condition, while ser is used for something more permanent or defining.

Here, sem sono means the speaker’s current condition: they are not sleepy right now. That is temporary, so Portuguese uses estar:

• estou sem sono = I’m not sleepy / I don’t feel sleepy

Using sou here would sound wrong, because being without sleepiness is not a permanent characteristic.

Literally, sem means without, and sono means sleepiness or sleep in this kind of expression.

So estou sem sono literally means I am without sleepiness, but in natural English it usually means:

• I’m not sleepy
• I’m not tired
• I don’t feel sleepy

A very common opposite expression is:

• estou com sono = I’m sleepy

So Brazilian Portuguese often expresses this idea with com sono / sem sono, rather than with a single adjective exactly equivalent to English sleepy.

They are very close in meaning.

• Estou sem sono = I’m without sleepiness
• Não estou com sono = I’m not sleepy

In most situations, they mean basically the same thing. The first sounds a bit more like stating a condition directly; the second is simply negating com sono.

Both are natural in Brazilian Portuguese.

Yes. Hoje means today, and Portuguese allows some flexibility in word order.

These are all possible:

• Hoje eu estou sem sono, então vou estudar português.
• Eu estou sem sono hoje, então vou estudar português.
• Eu vou estudar português hoje porque estou sem sono.

Putting Hoje at the beginning gives it a little more emphasis, like As for today... or Today...

Here, então means something like:

• so
• therefore
• then

In this sentence, it connects the two ideas:

• I’m not sleepy
• so I’m going to study Portuguese

It shows a result or consequence. In conversation, então is extremely common and useful.

The comma separates two connected parts of the sentence:

• Hoje eu estou sem sono
• então vou estudar português

This is very natural punctuation in Portuguese when então introduces the consequence of the first clause. It helps show the pause and logical connection.

Vou estudar is the very common near future construction in Portuguese:

• vou + infinitive

It corresponds to I’m going to study and is extremely common in everyday Brazilian Portuguese.

So:

• vou estudar = I’m going to study / I will study

The simple future estudarei is correct, but in spoken Brazilian Portuguese it often sounds more formal, more written, or less conversational.

In Brazilian Portuguese, the normal structure is:

• ir + infinitive

So you say:

• vou estudar
• vou comer
• vou dormir

You do not normally add a before the infinitive in standard Brazilian Portuguese.

In Portuguese, names of languages, nationalities, and many related adjectives are usually written with lowercase letters, unlike in English.

So Portuguese writes:

• português
• inglês
• brasileiro
• americano

This often surprises English speakers, because English would capitalize Portuguese and English.

The accent in português shows the stressed syllable and helps distinguish the correct pronunciation.

• portuGUÊS

Without the accent, the word would not follow normal spelling expectations. The accent marks the stressed final syllable with the ê sound.

The same is true for então, where the accent helps indicate pronunciation and stress.

In Brazilian Portuguese, então is roughly pronounced like en-TAŨ, with stress on the second syllable.

A few important points:

• The ão is a very common Portuguese nasal sound.
• It does not sound exactly like English ow.
• The final sound is nasal, meaning some air also passes through the nose.

English speakers often need practice with ão, because it appears in many common words:

• não
• então
• pão
• irmão

A rough pronunciation guide is:

• sem ≈ seng with a nasal vowel, not a full English m
• sono ≈ SOH-noo with stress on the first syllable

So the phrase is roughly:

• sẽj SO-no

The hardest part for many learners is sem, because the vowel is nasalized. In natural speech, the final m does not sound like a strong English m.

Because in this expression, sono is being used in a general, abstract way.

• sem sono = without sleepiness

Portuguese often omits the article in fixed expressions like this. Adding o here would sound unnatural in normal usage.

You can think of sem sono as a set expression, just like:

• com fome = hungry
• com sede = thirsty
• com pressa = in a hurry
• com sono = sleepy

In general, yes, português can mean different things depending on context:

• a língua portuguesa / português = the Portuguese language
• um português = a Portuguese man
• uma portuguesa = a Portuguese woman
• português as an adjective = Portuguese

In this sentence, estudar português clearly means to study the Portuguese language.

Yes, very natural. It sounds like everyday spoken Brazilian Portuguese.

Especially natural features are:

• eu estou / estou
• sem sono
• então
• vou estudar

A Brazilian speaker could easily say this in real life. An equally natural variation would be:

• Hoje não estou com sono, então vou estudar português.

Yes. The structure is very flexible:

• Hoje eu estou sem sono, então vou estudar matemática.
• Hoje eu estou sem sono, então vou estudar inglês.
• Hoje eu estou sem sono, então vou trabalhar.
• Hoje eu estou sem sono, então vou ler.

So the pattern to remember is:

• Hoje + (eu) + estou sem sono, então vou + infinitive