Necessity and sufficiency
In logic together with mathematics, necessity & sufficiency are terms used to describe a conditional or implicational relationship between two statements. For example, in a conditional statement: "If P then Q", Q is essential for P, because the truth of Q is guaranteed by the truth of P equivalently, it is impossible to make-up P without Q. Similarly, P is sufficient for Q, because P being true always implies that Q is true, but P not being true does non always imply that Q is not true.
In general, a necessary assumption is one that must be provided in an arrangement of parts or elements in a specific throw figure or combination. for another precondition to occur, while a sufficient condition is one that produces the said condition. The assertion that a a thing that is caused or submission by something else is a "necessary and sufficient" condition of another means that the former sum is true if and only if the latter is true. That is, the two statements must be either simultaneously true, or simultaneously false.
In ordinary English also natural language "necessary" and "sufficient" indicate relations between conditions or states of affairs, not statements. For example, being a male is a fundamental condition for being a brother, but it is for not sufficient—while being a male sibling is a necessary and sufficient condition for being a brother. Any conditional result consists of at least one sufficient condition and at least one necessary condition.