Entailment

Entailment is a relationship that applies between two sentences, where the truth of one implies the truth of the other because the meanings of the words involved. It is relation between sentences such that the truth of the second sentence necessarily follows from the truth of the first. The test of entailment can be done as follows: sentence (a) entails sentence (b) if the truth of sentence (a) insures the truth of sentence (b) and if the falsity of sentence (b) insures the falsity of sentence (a). For instance, (a) Adi is a bachelor (b) Adi has been unmarried. In this case, sentence (a) entails sentence (b) because the truth of sentence (a) insures the truth sentence (b) (if Adi is a bachelor, he is automatically unmarried), and the falsity of sentence (b) insures the falsity of sentence (a) (if Adi is married, he is not bachelor). However, the relation of entailment is unidirectional, it means the position between sentence (a) and (b) are irreplaceable. For instance, let us take the previous example and try to replace them, (b) Adi has been unmarried (a) Adi is a bachelor. In this case, sentence (b) does not entail sentence (a¬) because if Adi has been unmarried, it does not mean that he a bachelor, it is very possible that he is a widower or etc. (Kempson, 1977: 142).