Sui generis
Sui generis (; ) is a Latin phrase that means "of its (his, her, their) own kind; in a class by itself; unique."
Suum cuique
The Latin phrase relates to an old Greek principle of justice which translates literally into English as "to each his own". Plato, in "Republic", offers the provisional definition that "justice is when everyone minds his own business, and refrains from meddling in others' affairs" (Greek: "...τὸ τὰ αὑτοῦ πράττειν καὶ μὴ πολυπραγμονεῖν δικαιοσύνη ἐστί...", 4.433a). Everyone should do according to his abilities and capabilities, to serve the country and the society as a whole. Also, everyone should receive "his own" (e.g., rights) and not be deprived of "his own" (e.g., property) (433e).