Necessity and sufficiency

In logic, mathematics, and philosophy, the concepts of necessity and sufficiency are used to describe relationships between statements, conditions, or events. ### Necessity A condition \( A \) is said to be **necessary** for another condition \( B \) if \( B \) cannot be true unless \( A \) is also true. In other words, if \( B \) is true, then \( A \) must be true as well.