Learn Hardcore Portuguese (Portugal): Hoje é o dia em que eu estudo português com o Pedro. - Today is the day when I study Portuguese with Pedro.

In the sentence Hoje é o dia em que eu estudo português com o Pedro, you are identifying which day today is: it is the day on which I study…. This is a permanent characteristic of today in that context, so ser is correct.

Estar would sound wrong here. You use estar for temporary states or locations, not for naming or defining the day itself.

Why do we say em que instead of just que?

Em que is a relative construction that literally means in which / on which. The full idea is:

Hoje é o dia em que eu estudo…
→ Today is the day on which I study…

Here’s what is happening:

dia requires the preposition em for the idea on that day.
que is the relative pronoun that replaces o dia.

So you combine the preposition and the relative pronoun: em + que → em que.

You will also hear Hoje é o dia que eu estudo português…, especially in speech, but em que is more careful and grammatically precise, because it keeps the needed preposition.

Could I say Hoje é o dia quando eu estudo português com o Pedro?

This sounds wrong or at least very odd in European Portuguese.

Quando is mainly used as a conjunction introducing a time clause, not as a relative pronoun after a noun like dia in this structure.
English allows the day when…, but Portuguese normally uses em que or no qual in this position.

So the natural options are:

Hoje é o dia em que eu estudo português com o Pedro.
Hoje é o dia no qual eu estudo português com o Pedro. (more formal)

Avoid o dia quando… here.

Why is there an o before dia and also an o before Pedro?

These two o’s have different roles.

o dia
- o is the masculine singular definite article (the).
- Hoje é o dia… → Today is the day… (a specific day)
o Pedro
- In European Portuguese, it is very common to use the definite article before personal names, especially in everyday speech:
  - o Pedro, a Maria, o João, a Ana, etc.
- It does not mean the Pedro in English; it is just a normal, natural way to refer to people.

You might also see or hear the name without the article (Hoje é o dia em que eu estudo português com Pedro.), but in Portugal including the article (com o Pedro) is very typical and usually sounds more natural.

Why is eu included? Can I say …em que estudo português… without eu?

Portuguese is a null-subject language: the verb ending already shows who the subject is, so you can omit eu:

…em que estudo português com o Pedro. – also correct

Using or omitting eu depends on context:

With eu:
- Adds emphasis or contrast: Hoje é o dia em que eu estudo… (not someone else).
- Clarifies the subject if needed.
Without eu:
- Feels slightly more neutral and is very common in fluent speech and writing when the subject is obvious from the verb form.

So both are grammatically fine here; eu is not strictly required.

What does the tense eu estudo express here? Is it something I am doing right now or something habitual?

Eu estudo is the present simple of estudar. It can express:

Habit or routine (most likely here):
- Hoje é o dia em que eu estudo português com o Pedro.
  → There is a regular arrangement (for example, every Tuesday you study with Pedro).
An action happening now, depending on context:
- Agora eu estudo português com o Pedro. – Right now I am studying with Pedro.

In your sentence, the pattern é o dia em que… strongly suggests a habitual meaning: this is the usual day set aside for that activity.

Why is português not capitalized?

In Portuguese:

Names of languages are written with a lowercase initial:
- português, inglês, francês, alemão, etc.
Nationalities used as adjectives are also lowercase:
- um aluno português, uma família inglesa

The word Português with a capital P is only used as a proper noun, for example the subject in a school timetable or in a title:

A aula de Português começa às 10. – The Portuguese class starts at 10.
Dicionário de Português.

In your sentence, português is the name of the language in general, so it stays lowercase.

Is português here an adjective or a noun?

In eu estudo português com o Pedro, português functions as a noun: it is the thing you study (the language).

Compare:

Eu estudo português. – I study Portuguese (the language).
Eu sou português. – I am Portuguese (nationality, adjective).
Ele é um professor de português. – He is a Portuguese teacher (here português is more like a noun meaning the subject taught).

So in your sentence, português is the direct object of estudo.

Why is the word order português com o Pedro and not com o Pedro português?

The usual neutral order for a simple verb phrase in Portuguese is:

[verb] + [direct object] + [other complements (like prepositional phrases)]

In your sentence:

estudo = verb
português = direct object (what you study)
com o Pedro = prepositional phrase (with whom)

So the natural order is:

eu estudo português com o Pedro.

If you said eu estudo com o Pedro português, it would sound like:

I study with Portuguese Pedro (as if português were describing Pedro), which is not the intended meaning.

Can I say Hoje eu estudo português com o Pedro instead of the longer Hoje é o dia em que eu estudo…?

Yes, but the nuance changes.

Hoje eu estudo português com o Pedro.
- Means Today I am studying / I study Portuguese with Pedro.
- It focuses on the action happening today. It could be a one‑off or part of a routine; context decides.
Hoje é o dia em que eu estudo português com o Pedro.
- Emphasizes that today is that special/regular day designated for studying Portuguese with Pedro.
- It often implies a routine (for example, every Wednesday).

Both are correct; the second one highlights the idea of this particular day being the study day.

Is com always necessary to say with? Could I just say …eu estudo português o Pedro?

You must keep com here:

com = with
eu estudo português com o Pedro = I study Portuguese with Pedro

Without com, the sentence changes meaning or becomes incorrect:

eu estudo português o Pedro
- This is wrong; it looks as if o Pedro were another direct object of estudo, like I study Portuguese Pedro, which makes no sense.

So any time you mean with (a person), you need com:

Eu falo com o Pedro. – I speak with Pedro.
Eu trabalho com o Pedro. – I work with Pedro.

Is it possible to replace em que with no qual? What is the difference?

Yes, you can say:

Hoje é o dia no qual eu estudo português com o Pedro.

Here:

no qual = em + o + qual → literally in which (masculine singular, agreeing with dia)

Difference in feel:

em que
- Very common, natural, and neutral in both speech and writing.
no qual
- Grammatically correct but more formal / written.
- Often found in legal texts, academic writing, or very careful prose.

In everyday conversation, em que is the best choice.

How would this sentence typically sound in fast European Portuguese speech? Anything I should know about pronunciation?

A typical European Portuguese pronunciation (simplified) will have some linking:

Hoje é o dia em que eu estudo português com o Pedro.

Some points:

em que eu often flows together:
- The m in em is mostly nasalization; you will hear something close to ẽ quêu.
The eu is a single syllable, similar to “eh-oo” squashed together.
português ends with a strong ês sound; the final s is pronounced like an English sh in many European accents: portuguêsh.
The o in o Pedro is usually very short, almost like a light u in put.

Even if you do not pronounce it exactly like a native, keeping all the words (especially em que) is important for being understood clearly.