well I know it's Polish, but I mean like is there an original Polish word for "definicja"? (like emocja is uczucie and generacja is pokolenie etc.)
I do not think we have one. It's like "emocja" and "generacja" are those fancy words that only books use, but definicja is just normal word.
I mean we have opis=description, and wyjaśnienie=explanation, and określenie (noun from określać= determine, specify), and maybe those were enough for casual people and all scientiscts and lawyers and ther educated people whoneeded a word for definicja had that latin based word so it was much more spread then word for feelings and family history.
Ja kocham, ty kochasz, on kocha etc. To jest miłość Verb vs. Substantive (noun) No formal distinction in English