Yes. Or to put it differently: Instrumental is used as an aswer to question Who/What is he/she/it? and Nominative to answer questions What is he/she/it like?.
I still don't understand why smaczna doesn't take instrumental ending after 'jest'. Earlier lessons showed adjectives changing. ex: I am a small boy=jestem małym chłopcem I am a small girl=jestem małᶏ dziewczynkᶏ . I learn a lot from your usual comments, so am I missing something here?
The problem is that "am" means two different things in the two cases. It's not really the same "am."
In "I am a small boy," the copula "am" indicates the subject's identity as a member of a category. It means that "I" and "a (specific) small boy" are the same thing. In this situation, Polish uses the instrumental case for the predicate.
In "The sandwich is tasty," the copula is connecting "sandwich" with a description of one of its properties. "The sandwich" and "tasty" are not the same thing; "tasty" is just a description of the sandwich.
So I understand that "The" or "A" is hidden in this language but what if I am talking very generally about sth ? like how do i say "Sandwich is tasty" in polish ? just like when i wanna say "Pizza is delicious" ...
You could say just kanapka jest smaczna or pizza jest pyszna (and in some contexts it would be enough) or more often use plural (meaning the general collective of such things): kanapki są smaczne, pizze są pyszne.
But it really depends on context, if you argue with somebody about the taste of a general pizza, either of those would be probably OK.
Thanks a lot! so should i report it ? I wrote " sandwich is tasty" and Duo didn't accept it.
Even though Polish doesn't have articles, you need to use them while translating into English, so it should be a/the sandwich is tasty.
Further: English also uses the plural for statements of general truth, so had it been "sandwiches are tasty" you would have been okay.
What silmeth said, plus "Kanapka jest smaczna!" can be translated either as "Sandwich is tasty", "A sandwich is tasty"or "The sandwich is tasty" depending on the context. But if you want to stress that this particular sandwich is tasty (Which in English you would do either by saying "The sandwich is tasty!" or "This sandwich is tasty!") in Polish you'd say "Ta kanapka jest smaczna!" ("ta" = "this")
so why did the previous user say "Kanapka jest smaczna!" can be translated either as "Sandwich is tasty"