How similar are Portuguese and Spanish?

Answer 1

Originally, they were dialects of Latin, under the Roman Empire. Portuguese and Spanish evolved into two separate languages, with different sounds and vocabulary, etc. However, they evolved in isolation due to the fact that they were more or less isolated on the Iberian peninsula. Because of that, they are more similar to each other than any other of the romance languages.

I speak Spanish. I once had neighbors that just moved to the US from Brazil. They did not know English, so were really didn't have a common language. However, we found that were able to have basic communication when they spoke Portuguese and I answered in Spanish. It isn't ideal, of course, and depends on how well you pick up on languages. It is usually easier to read the other language than speak or understand it spoken, because you do not have the interference of different pronunciations that way.

I hope this answers your question!