AND = "A" when there is any type of contradictory between both parts:
- "I love you and you love him" - "Ja kocham ciebie a ty (kochasz) jego."
- "He cooks and she cleans the house" - "On gotuje a ona sprząta dom"
- "She is young and he is old" - "Ona jest młoda a on (jest) stary." (In the phrases containing contradiction, the repeated verb can be omitted). BUT: if the contradiction is not real, you only use different words to describe similar state, you go into nuances: "He is old and she is also not quite young" - "On jest stary a ona też niemłoda" (there is however some age difference between them, so she is younger than him) or "On jest stary i ona też niemłoda" (they are pretty similar, only you want to be polite and do not use the word "old" to describe a woman).
- "Her blouse is white and her skirt is red" - "Jej bluzka jest biała a jej spódnica (jest) czerwona." - it is so when the used verb is concerns the clothes itself, not the person who wears them; It works the same for longer lists: "Her hat is blue, her blouse is white, her skirt is red and her shoes are black" - "Jej kapelusz jest niebieski, bluzka biała, spódnica czerwona a buty czarne." see also below
AND = "I" when there is clear connection between both parts:
- "I love you and you love me" - "Ja kocham ciebie i ty kochasz mnie." (Attention, in this very case it would be also correct "Ja kocham ciebie a ty mnie", to underline sort of dualism: "you"-"me", while usage of i underlines the mutual similarity. With the usage of a, the repeated verb should be omitted).
- "He cooks and she cooks, too" - "On gotuje i ona też." or "On gotuje i ona też gotuje." or "On gotuje i ona gotuje."
- "She is young and he is young" - "Ona jest młoda i on jest młody."
- "Her blouse is white and her skirt is white" - "Jej bluzka jest biała i jej spódnica jest biała." or "Jej bluzka jest biała i jej spódnica też."
- BUT: when you enumerate the parts of clothing that somebody wears i.e. it is about the person, and not about one's clothes, you rather use i no matter, whether they are similar or different (as there is no contradictory within the person itself, and the verb relates to the person, not the clothing): "She wears a white blouse and a white skirt" - "Ona nosi białą bluzkę i białą spódnicę."; "She wears a white blouse and a red skirt" - "Ona nosi białą bluzkę i czerwoną spódnicę."
When there is any type of contradictory between both parts: Why use "and" instead of "but"? Or are they interchangeable?
I follow this rule and, as far as I know, I haven't missed anything yet:
If in English, you can use either but or and without changing the meaning, use "a."
If you must use but, use ale.
If you must use and, use i.
The only exception I know of is if you say something like, "And you?" Instead use "A Ty?"
It's common to use "a" when you compare two different activities, for example "My kupujemy, a oni sprzedają", "Ona pracuje, a oni śpią", "Ja biegnę, a ty nie (biegniesz)". "I" can be used for the same activity ("Ja lubię i ty lubisz", "Ja czekam i oni czekają") or when you list something ("Lubię biegać, spać i jeść").
Why can't I used but here? "a" could be but or and, correct? They way I understood it, if you can use but instead of and, you can use "a" in Polish. Is this wrong?
I don't see a reason to use "but". Those two things happen at the same time and are joined by "and". There is contrast, but it's visible in "a". We'd write "ale" or "lecz" if we wanted it to mean "but". But this sentence just states two facts.
My point is only that this sentence could be either "We are buying and they are selling." or "We are buying but they are selling." Either one should work for this sentence.
I agree with Zagadka314 because of the contrast between buying and selling. I really think 'but' is as good as 'and' here.
I think that in this sentence it really should be "ale" for "but", but okay, if several people want it I guess it won't harm... added.