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.
Jeffreys, H. and Jeffreys, B. S. "Necessary: Sufficient." §1.036 in Methods of Mathematical Physics, 3rd ed. Cambridge, England:
Cambridge University Press, pp. 10-11, 1988.
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