Definition:Circular Definition

Definition

A circular definition is a definition of a concept $A$ in terms of another concept $B$ such that the definition of $B$ itself refers (either directly or indirectly) to the definition of $A$.

It is a truism that circular definitions are always to be avoided.

Example

• "An integer is an element of an isomorphic copy of the inverse completion of the set of natural numbers."
• "A natural number is a positive integer."

Also known as

• A circular definition is also known as a vicious circle in the definition.

Also see

• Definition:Circular Proof
• Definition:Undefined Term

Sources

• 1946: Alfred Tarski: Introduction to Logic and to the Methodology of Deductive Sciences (2nd ed.) ... (previous) ... (next): $\S \text{II}.11$: The formulation of definitions