"Excuse me, but I have plans."
Translation:Извините, но у меня есть планы.
Based on my little understanding and experience, I have encountered "а" only in the context of comparison and contrasting between two things (e.g "Это девушка а не мальчик"). And. "но" Is used in the case of explaining a reason or a digression of some sort (e.g "Я хочу ем но у меня нет посуды").
From the Tips and Notes, and other comments, но is used for contradiction, which is easily read into the text here: whomever is being addressed apparently wants the speaker to do something, but the speaker is saying, "Sorry [I can't do that], I have plans."
I don't see "a" as relevant, because it's about contrasts and comparisons, e.g., я мальчик, а она девочка - there's no contradiction here at all, merely a comparison.
Yes, it is. And "извини" came from two words "из" (out of) and "вины (моей вины)" (my fault). That's why psychologists give advice to speak "прости" instead of "извини". The whole thing in the subconscious. But in life both words mean the same thing and none is more popular than the other.
the marks for pronunciation might seem trivial but it's a huge part of language, pronouncing "through" the same as "trough" bc one is just missing the first "h"? no-go!
you can download the Cyrillic keyboard for both android and iPhone for free in phone settings. recommend that to start!
If you are using the sentence structure "У меня/тебя/... есть [...] ", whoever has the thing (me, you, etc.) is in genitive. The subject in this case is what is had (the [...] ). If you are saying somebody does not have something, "У меня/тебя/... нет [...]" then both me/you/... and [...] are in the genitive.
Had to look it up, same question for me. Here is a very good explanation on а, но, и, тоже: http://learnrussian.rt.com/grammar-tables/conjunctions/