Learn Hardcore Portuguese (Portugal): Um dos meus amigos estuda português.

Even though amigos is plural, the expression um dos meus amigos is treated as a singular subject (one friend out of the group), so the verb must be in the 3rd person singular:

ele estuda (he studies) → um dos meus amigos estuda

If you made it plural:

Alguns dos meus amigos estudam português.
(alguns = some, plural → estudam = they study)

Why do we say meus amigos and not meu amigos?

In Portuguese, possessive adjectives agree in gender and number with the noun they describe, not with the owner.

amigo (friend, masculine singular) → meu amigo (my friend)
amigos (friends, masculine plural) → meus amigos (my friends)
amiga (friend, feminine singular) → minha amiga (my friend)
amigas (friends, feminine plural) → minhas amigas (my friends)

So here:

noun: amigos (masculine plural)
possessive: meus (masculine plural)

Therefore, meus amigos is correct; meu amigos is ungrammatical.

What exactly is dos in um dos meus amigos? Why not just de?

dos is a contraction of de + os.

The full underlying structure is:

um de os meus amigos → contracted to → um dos meus amigos

In natural Portuguese, the preposition de usually contracts with the definite article that follows it:

de + o = do
de + a = da
de + os = dos
de + as = das

So um dos meus amigos literally means one of the my friends → “one of my friends.”
Saying um de meus amigos is possible but sounds more formal or literary in European Portuguese. In everyday speech, um dos meus amigos is the normal choice.

Can I also say Um amigo meu estuda português? Does it mean the same thing?

Yes, Um amigo meu estuda português is correct, and the meaning is very close, but there is a nuance.

Um dos meus amigos estuda português.
Emphasises “one of my friends (from the group of my friends)”. It feels slightly more specific.
Um amigo meu estuda português.
Literally “a friend of mine studies Portuguese”.
This sounds a bit more indefinite or casual, as if you’re just mentioning that you happen to have a friend who studies Portuguese, without focusing on the idea of a defined group.

Both are perfectly natural in European Portuguese; the difference is subtle and often not important in casual conversation.

Why is português not capitalised in this sentence?

In Portuguese, names of languages are written with a lowercase initial letter.

português (Portuguese)
inglês (English)
francês (French)
alemão (German)

So:

Ele estuda português. ✅
Not: Ele estuda Português. ❌ (this looks wrong to a native speaker)

By contrast, nationalities used as nouns for people can be capitalised in some contexts (especially in official or formal writing), but language names normally are not capitalised in standard usage.

If the friend is a woman, does the sentence change?

To make it clearly about a female friend, you would normally change the article, possessive, and noun to the feminine:

Uma das minhas amigas estuda português.
→ One of my (female) friends studies Portuguese.

Changes:

Um → Uma (masculine → feminine)
meus → minhas (masculine plural → feminine plural)
amigos → amigas (masculine plural → feminine plural)

The verb estuda stays the same because 3rd person singular (he/she) has the same form.

Could I say está a estudar português instead of estuda português? What’s the difference?

Yes, you can say:

Um dos meus amigos está a estudar português.

In European Portuguese:

estuda português (present simple)
Often used for habits, ongoing activities, or general facts. It can mean:
- He studies Portuguese (as a subject, regularly).
- He is studying Portuguese (general statement).
está a estudar português (present progressive)
Focuses more on the action as in progress at this period or right now:
- He is in the process of studying Portuguese (these days / at the moment).

In everyday European Portuguese, the simple present (estuda) already covers both ideas very often. Está a estudar just adds a bit more emphasis on the ongoing nature of the activity.

Why is there no article before português? Why not estuda o português?

Both forms exist, but they are used a bit differently.

Ele estuda português.
Very common, especially when talking about learning the language in general:
- He studies Portuguese / He is learning Portuguese.
Ele estuda o português.
Possible, but tends to sound more formal or specific, for example in academic or very precise contexts, like:
- He studies the Portuguese language (as an academic subject, linguistics, philology, etc.)

For an ordinary learner of the language, Ele estuda português is the standard, natural way.

What is the grammatical role of português here? Is it a noun or an adjective?

In this sentence, português is a noun meaning “the Portuguese language.”

Verb: estuda (studies)
Direct object: português (Portuguese, the language)

Português can also be an adjective:

um amigo português = a Portuguese friend (friend who is from Portugal)
a língua portuguesa = the Portuguese language

In estuda português, it functions as a noun (“studies Portuguese [language]”).

Can I drop meus and just say Um dos amigos estuda português?

You can say Um dos amigos estuda português, but the meaning changes.

Um dos meus amigos estuda português.
→ One of my friends studies Portuguese.
Um dos amigos estuda português.
→ One of the friends studies Portuguese.

The second version sounds like you are referring to a group of friends that has already been mentioned or is understood from context, not necessarily your friends. For example:

Eles são um grupo muito unido. Um dos amigos estuda português.
“They are a very close group. One of the friends studies Portuguese.”

If you want to include the idea of “my,” keep meus.

If I say Um dos meus amigos portugueses estuda…, is that different from the original sentence?

Yes, adding portugueses after amigos changes the meaning.

Um dos meus amigos estuda português.
→ One of my friends studies Portuguese (the language).
Um dos meus amigos portugueses estuda…
→ One of my Portuguese friends (friends who are Portuguese) studies…

Here:

português right after estuda → language
portugueses after amigos → adjective describing the friends (their nationality)

So be careful with word order and endings:
amigos portugueses = Portuguese friends (people)
estuda português = studies Portuguese (language)

How is Um dos meus amigos estuda português pronounced in European Portuguese?

Approximate breakdown (European Portuguese):

Um – nasal sound, similar to French “un”; often very short, like a nasal u.
dos – sounds like “dosh” (the s at the end is often pronounced /ʃ/ in European Portuguese).
meus – roughly “meush” (again, final s as /ʃ/).
amigos – a-MI-gush (stress on MI, final s as /ʃ/).
estuda – esh-TU-da (initial e often like “ish”, stress on TU).
português – por-tu-GUÊSH (stress on the last syllable guês, final s as /ʃ/).

Connected, it flows something like:

“Um dos meush amigos esh-TU-da por-tu-GUÊSH.”

In natural speech, some vowels may be reduced or almost swallowed, especially the unstressed ones.