Here is what I found from Google. I really feel like… it’s hard as hell and I don’t get it. I only know because vs why and they don’t even seem to put enough emphasis on the fact that its entirely different word (why vs because) So I am still lost but it helps a bit? I like to just write the super informal “pq” when talking. I believe it’s slang. Means the same thing but you don’t have to figure out if its the right one or not.
Por quê (two words, with circumflex accent on ‘e’) can only occur at the end of an indirect or direct interrogative phrase:
Eileen didn’t arrive yet, why? Eileen didn’t arrive yet, no one knows why.
- Interrogação direta: Eline não chegou ainda, por quê?
- Interrogação indireta: Eline não chegou ainda, ninguém sabe por quê.
Por que (two words, no accent) can be used in two situations:
Why didn’t Guy call yesterday? No one knows why Guy didn’t call yesterday.
- To start an interrogative, direct or indirect:
- Direct: Por que Gui não ligou ontem?
- Indirect: Ninguém sabe por que Gui não ligou ontem.
- When it could be substituted for: pelo qual, pela qual, pelos quais, pelas quais :
- Desconhece-se a razão por que (pela qual) Gui não ligou.
It’s Unknown the reason why Guy didn’t call.
Porquê / Porquês (one word, with an accent circumflex on the ‘e’) is the right way to form the noun. It is easy to spot, since it will always be preceded by an article: o, a, os, as, da, das, do, das, na, nas, no, nos, etc., demonstrative pronoun ( este, estes ), or an adjective:
- Desconhece-se o porquê da ausência de Marcos.
- O estudo dos porquês é interessante.
- Os estudantes se defrontam com muitos porquês.
Porque (one word, no accent) for when all else fails, and the use fits none of the previous categories: O Gui não ligou porque estava fora da cidade.
This one is just “because” // Guy didn’t call because he was out of town.