Quote Originally Posted by Seraph View Post
Prunus cerasus sour fruit, for cooking, is pie cherry. Prunus avium is sweet cherry, for eating fresh right of tree.
Thank you! Yes, I agree, I think вишня is indeed sourer than черешня.
BTW, although your explanation may work perfect for English speakers, in Russia we do also eat вишня fresh right of tree. But we can use it for cooking as well (cherry pie etc.). So, both kinds of cherry are eaten fresh

Quote Originally Posted by Seraph View Post
Logic itself might be mass noun логик, (unless different types of logic are the topic? разные логики?).
In Russian, логика is feminine: Мне непонятна твоя логика (Your logic is unclear to me). Yes, it is a mass noun.
Yes, different types of logic is логики. This term is used in plural in abstract logic theory, for different logics with different sets of axioms.