Learn Hardcore Portuguese (Portugal): Ontem fiz a inscrição num clube de leitura com horário fixo às segundas. - Yesterday I registered in a book club with a fixed schedule on Mondays.

Eu fiz a inscrição num clube de leitura… – perfectly correct, a bit more emphatic on I.
Fiz a inscrição num clube de leitura… – more natural in everyday speech and writing.

So the sentence omits eu because it’s understood from the verb form.

What does fiz a inscrição literally mean, and why use fazer here instead of a verb like inscrever?

Fiz a inscrição literally means “I did the registration / I did the enrollment.”

Portuguese often uses fazer + noun instead of a single specific verb, especially with nouns like:

fazer a inscrição – to do the registration / sign up
fazer a reserva – to make the reservation
fazer a matrícula – to enroll (in a course/school)

A more “verb-like” alternative is:

Ontem inscrevi‑me num clube de leitura… – Yesterday I enrolled / signed up for a reading club…

Both are natural in European Portuguese:

fiz a inscrição – focuses on the action of completing the registration process
inscrevi‑me – focuses more directly on enrolling myself

You’ll hear both in Portugal.

Why is it a inscrição and not o inscrição? How do I know the gender?

Inscrição is a feminine noun in Portuguese, so it takes the feminine article a:

a inscrição – the registration / enrollment

There isn’t a fixed rule that always tells you the gender from the ending, but:

Many nouns ending in ‑ção (from Latin ‑tione) are feminine:
- a inscrição (registration)
- a informação (information)
- a inscrição (registration)
- a tradução (translation)

So:

a inscrição – correct
o inscrição – incorrect

Could I say fiz minha inscrição like in Brazilian Portuguese, or do I need a in European Portuguese?

In European Portuguese, the most typical options here are:

Ontem fiz a inscrição num clube de leitura…
Ontem fiz a minha inscrição num clube de leitura…

Using the definite article with possessives is standard in European Portuguese:

a minha inscrição, o meu carro, a tua casa, etc.

So:

fiz a inscrição – common and natural
fiz a minha inscrição – also very natural, a bit more personal/explicit
fiz minha inscrição – sounds clearly Brazilian; not wrong, but unusual in European speech/writing

If your target is Portuguese from Portugal, prefer a inscrição or a minha inscrição.

What exactly is num? Is it different from em um?

Num is the contracted form of em + um:

em + um = num
em + uma = numa

They both mean “in a / at a / on a”, depending on context.

So:

num clube de leitura = em um clube de leitura = in/at a reading club

In European Portuguese, the contracted forms (num, numa) are much more common in speech and informal writing. Em um is grammatically correct but sounds more Brazilian or very formal.

Why is it clube de leitura and not something like clube de ler?

In Portuguese, when you want to say things like “reading club”, the most natural pattern is often noun + de + noun:

clube de leitura – reading club
grupo de estudo – study group
aula de piano – piano lesson

Using the infinitive ler (to read) here would sound odd:

clube de ler – not idiomatic

Leitura is the noun corresponding to ler, just like reading is the noun from to read in English. So clube de leitura is the natural phrase.

What does horário fixo add? Could I just say num clube de leitura às segundas?

Horário fixo means “fixed schedule / fixed time”.

com horário fixo às segundas = with a fixed time on Mondays

If you say only:

num clube de leitura às segundas

it’s still understandable, but it’s slightly less explicit. Horário fixo emphasizes that the meetings are always at the same set time every Monday, not changing week to week.

So:

With horário fixo – stresses the regular, unchanging time.
Without it – just says “on Mondays,” the regularity is implied but less explicit.

Why is it às segundas in the plural? Does that mean “every Monday”?

Yes. In Portuguese, using the day of the week in the plural usually means “every [that day]” / “on [those days] regularly”:

à segunda – on Monday (often a specific Monday, or sometimes “on Mondays” depending on context)
às segundas – on Mondays (in general, every Monday)
às sextas – on Fridays (every Friday)

So com horário fixo às segundas naturally suggests:

with a fixed schedule (meeting) every Monday

The plural here is the most straightforward way to express a repeated weekly event.

Why is it às segundas and not nas segundas? What’s the difference?

Both às segundas and nas segundas can be heard, but they’re not quite the same:

às segundas = a + as segundas
- emphasizes time / schedule: at/on Mondays
- very natural with schedules:
  - Trabalho das 9h às 17h.
  - Aulas às segundas e quartas.
nas segundas = em + as segundas
- more like on Mondays in the sense of “during Mondays / on that day”
- slightly less tightly connected to schedule expressions

In a context of a club with a fixed meeting time, às segundas sounds more idiomatic, because a is the preposition typically used for times and time ranges.

Could I also say à segunda-feira instead of às segundas?

Yes, you can. Common options (all understandable):

com horário fixo às segundas – very natural, “every Monday”
com horário fixo à segunda-feira – also correct, a bit more formal or explicit
com horário fixo às segundas-feiras – also possible, often sounds a bit more formal/written

Subtle feel:

às segundas – short, very common in speech
à segunda-feira / às segundas-feiras – slightly more formal or careful style, often used in written notices, timetables, etc.

Why is the verb in the past fiz and not something like fazia?

Fiz is the pretérito perfeito (simple past), used for a completed action at a specific time in the past:

Ontem fiz a inscrição… – Yesterday I completed the registration… (done, finished event)

Fazia is the pretérito imperfeito, which describes ongoing, habitual, or background past actions:

Quando era mais novo, fazia a inscrição em muitos clubes.
– When I was younger, I used to sign up for many clubs.

Here, we’re talking about one completed action yesterday, so fiz is the natural choice.

Is inscrição num clube correct without para? I’ve also seen inscrição para um clube.

Both structures exist:

inscrição num clube de leitura – literally registration in a reading club
inscrição para um clube de leitura – literally registration for a reading club

In practice:

inscrição num clube is very idiomatic in European Portuguese, especially when you’re already thinking of physically/officially being in that club.
inscrição para um clube emphasizes the idea of for the purpose of joining that club.

Neither is wrong; the version in your sentence (num clube) is perfectly natural.

How would this sentence typically be said in Brazilian Portuguese?

A natural Brazilian Portuguese version might be:

Ontem me inscrevi em um clube de leitura com horário fixo às segundas.

Main differences:

me inscrevi instead of inscrevi-me
- Brazilian Portuguese tends to place the clitic pronoun me before the verb.
em um clube instead of num clube
- num exists in Brazil, but em um / em uma are more common in standard writing and many speech varieties.
You might also see fiz minha inscrição instead of fiz a inscrição or fiz a minha inscrição, often without the article before the possessive.