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 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."