The French for Jock also means Sportsmen... If I understood, the plural is marked by the "i" at the end of the word, right ?
Is your game in english ? If it's in Serbian you can get the translations from there...
If the word ends with A, the last letter in plural is usually E, but that's not always the case (sportsman, sportista in Serbian, is both sportiste and sportisti in plural. Both can be used). When the word ends with a consonant, the last letter in plural is usually I. The word "doba" (age, season) is the only singular word in Serbian language, ending with A, which does not have a plural form. A season (winter, summer) is godišnje doba in Serbian (godishñe doba), and the plural is godišnja doba.
Did you know that the word vampire (Serbian spelling is vampir (vampeer)) is originally from Serbia? And it is the only Serbian word used by the whole world.
My game is in English, and I don't think a Serbian translation exists, but I'd love to have one!