Learn Portuguese (Portugal): O comboio parte na sexta-feira.

In English, we say "on Friday", but Portuguese uses the preposition em (in/on) combined with the word "the". All days of the week ending in -feira are feminine, so we use the feminine "the" (a). When you combine em + a, you get na. Literally, the sentence is saying "The train leaves in the Friday."

Do I always have to say the -feira part?

In spoken or casual Portuguese, people often drop -feira and simply say na sexta. However, it is important to know the full name because you will see it in writing, on official schedules, and in formal contexts.

What verb is parte and how does it work here?

Parte comes from the verb partir, which means "to leave" or "to depart". It is a regular verb ending in "-ir". Because the train (o comboio) acts as an "it", we use the third-person singular form, which ends in "-e" for regular "-ir" verbs.

I have seen the word "trem" for train before. Why are we using comboio?

Comboio is the standard word for "train" in European Portuguese. If you have seen "trem", that is the word used in Brazilian Portuguese. Since you are learning the Portuguese of Portugal, comboio is the word you will hear and use at the station!