Oi Alex,
Do we need to write "o Tom", or would "Tom" also be enough?
Is there a certain nuance with the use of "o", such as familiarity etc?

Ah, remember that it's not always "o". You use "o" for a man and "a" for a woman. So "O Tom gosta da Maria" and "A Maria gosta do Tom". OK?

> Is there a certain nuance with the use of "o", such as familiarity etc?
You can say so, but most people use it in spoken Portuguese. When it's about written Portuguese, it's just a matter of style. In newspaper and magazines, for example, you'll hardly see the article. I've been using it here because it makes the sentence much more natural and close to the spoken language.

Do you remember the possessive pronouns in Portuguese? It's just the same! You can say both "meu carro" and "o meu carro", "minha mãe" and "a minha mãe", "obedeço a meu pai" and "obedeço ao meu pai", "obedeço a minha mãe" and "obedeço à minha mãe".

Espero que tenha ajudado! :-)

Yes, you did!
I remember (of course, I remember also the "a" for feminine nouns). OK, so this reflects the spoken language.
Obrigado, amigo!

Sempre às ordens! ;-)

;-)