# If-and-only-if-it

If-and-only-if-it expresses biconditional logical connective between two statements. In the construction Something is ... if-and-only-if-it ... equivalent concepts are introduced. The concequent concept can be a complex concept. It allows to define new concept as intersection, union etc. of old ones. The construction can me modified to give complement concept.

### Examples

Those examples show how to define concepts.

Example: Equivalent concepts.

Something is a boy if-and-only-if-it is a young-male-man.

Example: Concept intersection.

Something is a young-male-man if-and-only-if-it is a young-thing and is a male-thing and is a person.

Example: Everything in the world is an adult-thing or a young-thing. The concepts are complement.

Something is a young-thing if-and-only-if-it is not an adult-thing.