Learn Hardcore Portuguese (Portugal): Eu escrevo uma frase no caderno.

Eu escrevo uma frase no caderno. – more explicit, can be used for emphasis or contrast.
Escrevo uma frase no caderno. – very natural, especially in context where it’s clear who is speaking.

In everyday speech, dropping the subject pronoun is very common.

What tense is escrevo? Does it mean I write or I am writing?

Escrevo is the present indicative of escrever (to write).

In Portuguese, this tense usually covers both:

I write (a general habit):
Eu escrevo frases no caderno todos os dias.
I am writing (right now / around now):
Eu escrevo uma frase no caderno neste momento.

So Eu escrevo uma frase no caderno can mean either I write a sentence in the notebook or I am writing a sentence in the notebook, depending on context.

If I want to say I am writing a sentence in the notebook (right now), is there a more explicit way to say it in European Portuguese?

Yes. In European Portuguese, the most natural explicit continuous form is:

Estou a escrever uma frase no caderno.

Structure:

estou – present of estar (to be)
a – particle
escrever – infinitive

So:

Eu escrevo uma frase no caderno. – neutral present; can be habit or now.
Eu estou a escrever uma frase no caderno. – clearly emphasizes the action is happening now.

(For comparison only: in Brazilian Portuguese it’s usually estou escrevendo, but in Portugal the normal form is estou a escrever.)

How is the verb escrever conjugated in the present tense?

Escrever (to write) – present indicative:

eu escrevo – I write
tu escreves – you write (singular, informal)
ele / ela escreve – he / she writes
você escreve – you write (formal singular, or neutral in some regions)
nós escrevemos – we write
vocês escrevem – you write (plural)
eles / elas escrevem – they write

So in your sentence, escrevo matches eu.

Why is it uma frase and not um frase?

Because frase is feminine in Portuguese.

Each noun has a grammatical gender:

a frase – the sentence (feminine)
uma frase – a sentence (feminine)

Compare:

o caderno – the notebook (masculine)
um caderno – a notebook (masculine)

So you must match the article to the noun’s gender:

uma frase (feminine)
um caderno (masculine)

What is the difference between uma frase and a frase?

Both refer to “sentence”, but:

uma frase – a sentence, one sentence, non‑specific:
Eu escrevo uma frase no caderno.
I write a sentence (not a particular one we’ve talked about).
a frase – the sentence, specific/known:
Eu escrevo a frase no caderno.
I write the sentence (that we already know / mentioned).

So uma = indefinite, a = definite, like a vs the in English.

What exactly is no in no caderno? Why not just em o caderno?

No is a contraction of the preposition em (in, on, at) + the masculine singular article o (the):

em + o = no
em + a = na
em + os = nos
em + as = nas

So:

no caderno = em o caderno = in the notebook
na mesa = em a mesa = on the table

In real Portuguese, people always use the contracted forms (no, na, nos, nas), not em o, em a, etc.

In English we would usually say in my notebook, not in the notebook. Why is it no caderno and not no meu caderno?

Portuguese often omits possessive adjectives (meu, minha, etc.) when the owner is obvious from context (especially with body parts, clothes, and personal objects).

Eu escrevo no caderno.
Literally “I write in the notebook”, but in a natural context this is often understood as “in my notebook”.

If you need to be explicit, you can (and sometimes should) say:

Eu escrevo no meu caderno. – I write in my notebook.
Eu escrevo no teu caderno. – I write in your notebook (informal tu).
Eu escrevo no seu caderno. – I write in your / his / her notebook (depends on context).

So no caderno is fine and common when it’s clearly your own notebook.

Can I change the word order? For example, can I say Eu escrevo no caderno uma frase?

Yes, Portuguese word order is fairly flexible, especially with adverbial phrases like no caderno.

All of these are grammatically possible:

Eu escrevo uma frase no caderno. – most neutral.
Escrevo uma frase no caderno. – also very natural.
Eu escrevo no caderno uma frase. – possible; sounds a bit more marked or “styled”.
No caderno, eu escrevo uma frase. – emphasizes no caderno (In the notebook, I write a sentence).

For basic sentences, stick with the neutral order: (Eu) escrevo uma frase no caderno.

How do I make this sentence plural, like I write sentences in the notebook?

You mainly need to pluralize the noun:

Eu escrevo frases no caderno.
I write sentences in the notebook.

Notes:

frase → frases (add -s)
Indefinite plural umas frases (some sentences) is possible but often dropped:
- Eu escrevo umas frases no caderno. – I write some sentences (a few, some, often with a nuance of “a couple of”, “a handful of”).

So:

uma frase → frases (or umas frases)
The verb escrevo does not change because the subject eu is still singular.

Is frase exactly the same as “sentence” in English? What about sentença?

Not exactly.

frase – the normal word for a sentence (in grammar) or phrase/line of text or speech.
- Eu escrevo uma frase no caderno. – I write a sentence in the notebook.
sentença – usually means a legal sentence (verdict, judgment) or a set phrase/aphorism:
- A sentença do juiz. – the judge’s sentence.
- uma sentença filosófica – a philosophical saying/maxim.

So for normal written sentences in language learning, you want frase, not sentença.

How is Eu escrevo uma frase no caderno pronounced in European Portuguese?

Approximate European Portuguese pronunciation (using English-like hints):

Eu – like “eh-oo” merged, closer to “ehw”.
escrevo – roughly “shk-REH-voo”
- initial e is unstressed and often reduced, and s between vowels or word-initial before consonant can sound like sh in many dialects.
uma – “OO-muh”
frase – “FRAH-ze” (final e is very reduced, almost like a quick “uh”).
no – “noo”, but short.
caderno – “kuh-DER-noo”, with a light r (tap) and reduced final o.

Very rough IPA (European Portuguese):
[ew ɨʃˈkɾɛvu uma ˈfɾaz(ɨ) nu kɐˈðɛɾnu]

Don’t worry about the exact sounds at first; focusing on sentence rhythm and stress (esCREvo, FRAse, caDERno) is a good start.