I have some questions.
I am interested in learning Portuguese. How similar are Portuguese and Spanish grammar, pronunciation, and vocabulary?
Also, what are the main differences between Brazilian Portuguese and Portuguese spoken in Portugal? Is Brazilian Portuguese influenced by Brazil's native peoples?
Lastly, is African Portuguese closer to Brazilian Portuguese or Portuguese spoken in Portugal?
If you know Spanish, that is a good platform to begin to learn Portuguese. Portuguese grammar is a little more complex than Spanish, with an interesting set of contractions, conjugated infinitives and -or verbs. It is pretty easy to learn a handful of rules to "portuguify" many Spanish words. Don't fall into the trap of thinking that Portuguese is a dialect of Spanish, though. I have to be reminded of that periodically.
I like to say I speak pretty decent portunhol.
Portuguese and Spanish have some similarities, and it's easier to learn Portuguese from Spanish than from English. Portuguese from Brazil and Portugal have some differences in accent and grammatical rules, but they are very similar. Brazilian Portuguese is influenced by a lot of other languages, like Spanish, Italian, even English. African Portuguese is closer of Portugal than Brazilian Portuguese.
Pronunciation/phonetics is really what sets PT and ES dramatically apart. In general Portuguese speakers are better at understanding Spanish than the other way around. The main reason is probably the number of phonetic vowels in Portuguese (9 versus 5 in ES) and quite a few of other phonetic issues that are too technical for me to explain. The result is that often Spanish speakers unused to listen to Portuguese can't even recognize it (I've witness these several times in my life, once I even heard a Spanish couple wondering if me and a friend were speaking Polish - true story).
Differences between PT-PT and PT-BR are constantly overrated throughout the internet... I believe the main reason for that is historical/political rather than the actual differences. Portugal is simply much smaller than Brazil, there's no other example of a former colonial power being so much smaller than the former colony. This leads to Brazilians being little aware of what's going on in Portugal and not consuming much Portuguese cultural products, so they're unused to listen to our accent and when a Brazilian listens to PT accent for the first time can be quite challenging. But the same can be said about a Lisboner listening to the accent from São Miguel island (Azores, PT). It's all a matter of getting used to it... thousands of Brazilians live nowadays in Portugal, and they all got used to it. On the other hand Brazilians in Portugal take many years to actually change their accent, while Portuguese people in Brazil very quickly adopt a more BR sounding accent - I believe this is simply due to the fact that for Portuguese people there are few mysteries on the Brazilian accent as we do consume a lot of Brazilian music/tv.
But things are changing, I'm surprised to see more and more Brazilian comments on Portuguese youtube videos for instance, people are curious and the internet can really work as a bridge.
Finally the African colonies were under Portuguese rule till 1975, so in general their way of speaking follows closely the Portuguese way. If you watch Angolan TV some of the presenters sound just like anyone in Lisbon. But there are strong social dialects, so the Portuguese spoken by political and cultural elites (often educated in Portugal) can sound very much like PT-PT, but the Portuguese on the street can sound very differently. Time will show how things will evolve, Brazilian cultural influence is growing a lot in these countries, and by 2100 the prediction is that most Portuguese speakers will be living in Africa, so this is very interesting to follow.
PS: A curiosity many people don't know, Portuguese is the language with the most native speakers on the Southern Hemisphere. Which shows the importance of Brazil, Angola and Mozambique in the demographics of Portuguese. Portugal is only the 4th country by population size on the Lusosphere.
I heard the difference is because of the time between the liberatiion of Spain and Portugal during the Reconquista. Portugal was liberated in 1168 while the south of Spain remained under dominion until 1492. A lot of difference in vocabulary comes from the Arabic influence in Spanish.
Portuguese was strongly influenced by a Celtic substratum due to the higher Celtic presence in Galicia, the place where the family tree of the language originated. Spanish shared the same Celtic substratum (albeit it wasn't as thick - Portuguese keeps nasal vowels, one of the features of their influence), but it was influenced by Basque for a longer term, and shares a few traits of Basque influence with Gascon, a dialect of Occitan. People tend to overestimate the importance of Arabic in Al-Andalus. Nowhere in Iberia ever truly felt like an Arabic country. Those Muslim kingdoms had their populational basis speaking Mozarabic, which is actually an extinct Romance language. It was like when India was ruled by Muslim elites but most of the population just kept being Indian and Hindu.
According to ethnologue.com, the lexical similarity coefficient between Spanish and Portuguese is 0.89, or about 89% shared vocabulary. By comparison, between Spanish and Italian is 0.82, between Spanish and French is 0.75, and between German and English is 0.60.
Portuguese does sound different to me than Spanish. Vowels sound very similar but consonant sounds are different. The Portuguese of Portugal sounds more like Spanish, to me, than the Portuguese of Brazil. I don't know about any of the African varieties.
FYI, ethnologue lists these variants of the Portuguese language:
Beiran (Beirão), Alentejan (Alentejano), Algarvian (Algarvio), Minhotan (Minhoto), Transmontan (Transmontano), Madeirese (Madeirense), Azorean (Açoriano), Estremenho, Brazilian Portuguese. Standard Portuguese of Portugal based on Estremenho dialect (Lisbon and Coimbra).
Portuguese and Spanish are similar in grammar, writing ,etc.. but different in pronunciation, Spanish pronunciation is simple there are few sound but portuguese is more complex and has more sounds. it's easier a portuguese speaker learns Spanish than a Spanish speaker learns portuguese because Spanish speakers need to learn new sounds ,some portuguese sounds don't exist in Spanish language.
Brazilians portuguese is used only in Brazil ,África and Asia countries use portuguese from Portugal. Portugueses, Angolans and Mozambicans can understand brazilian portuguese because they have contact with BR portuguese through the Brazilian channels, soap operas ( telenovelas) and musics. But Brazilians have difficult to understand africans, asians portuguese speakers and portugueses because brazilians don't have contact with TV's channels, movies or musics from theses countries.there are diferences in vocabulary and a bit in grammar structure alike happen between British english and American english.
Vocabulary between Portuguese and Spanish is similar but there are many false friends too .