Eu moro em, no, na?

[Joseph]

@Molly

“Na” is a contraction of “em + a”, so if you hear other people say “na” or “no” (or “do”/“da” instead of “de”), you know that that particular place uses a definite article when talking about it in a sentence. Sounds like there’s not a way to know for sure without looking it up or hearing someone say it.

This is it, @davidcowling949. The “na” already shows you that there’s a definite article there, it’s just contracted with "em’. And yeah, for the most part, you’ll have to listen for clues in other people’s conversations, if you don’t know in advance whether or not to use the definite article. If in doubt, feel free to stick to “em” until you figure out what people usually say.

@Molly

When in doubt, I try to use “em” for cities, “no”/“na” for countries, “no”/“na” for regions (e.g. “no Algarve”). Over time I learn more exceptions (e.g. It’s “em Lisboa”, but “no Porto”. It’s “em Portugal”, but “nos Estados Unidos”).

“O Porto” and “os Estados Unidos” can both be explained away by the common noun rule. Other exceptions are harder to make sense of. I do like your way of managing this! I can see it working well a lot of the time.