[2] Entailment contrasts with the pragmatic notion of implicature.
While implicatures are fallible inferences, entailments are enforced by lexical meanings plus the laws of logic.
[3] Entailments also differ from presuppositions, whose truth is taken for granted.
Unlike an entailment, presuppositions survive when the sentence is negated.
The negation test can be used to determine the difference between entailment and presupposition.