A Condition which, if true, guarantees that a result is also true. (However, the result may also be true if the Condition is not met.) If a Condition is both Necessary and Sufficient, then the result is said to be true Iff (``if and only if'') the Condition holds.
For example, the condition that a decimal number end in the Digit 2 is a sufficient but not Necessary condition that be Even.
See also Iff, Implies, Necessary