Defining {definition} can state class and distinction.
Definitions {impredicative definition}| {vicious-circle principle} can define objects in terms of object classes, a type of circular definition. The idea of set of all sets leads to such contradiction. Logical paradoxes can depend on impredicative definition.
Definitions {operational definition, logic} can be how to use words.
Definitions {predicative definition} can not quantify over all class objects.
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Date Modified: 2022.0225