Meaning relations among sentences
As we have seen with respect to words, sentences have meanings that can be analysed in terms of their relation to other sentences. The most important types of semantic relations among sentences are paraphrase, entailment, and contradiction.
Two sentences that have the same meaning are called paraphrases of each other. Thus, at the sentence level, paraphrases are the equivalent of synonyms at the lexical level. As with synonyms, there is often a stylistic difference between the sentences in question. Such sentences have a very similar (not necessarily the same) meaning. In terms of formal semantics, they can be described as having the same truth conditions, i.e. they are true under the same circumstances, and one cannot be true without the other sentence also being true: The dog chased the cat paraphrases The cat was chased by the dog.
If the truth of one sentence entails (or implies) the truth of the other sentence, the relation between those sentences is usually referred to as entailment. While paraphrases have the same truth conditions and always entail each other (symmetrical entailment), we speak of entailment when one sentence entails that the other sentence is true, but the reverse does not hold. Thus, many examples of entailment are based on hyponymy between lexical items: Mary loves flowers entails Mary loves roses.
There are also pairs of sentences that contradict each other. Here, the truth of one sentence implies the falseness of the other: if one sentence is true, the other is necessarily false. This kind of relation is referred to as contradiction or negative entailment. In many cases, the contradiction is based on antonymy between lexical items: It is cold in here contradicts It is hot in here.
Exercises on meaning relations among sentences
- Mary loves flowers entails Mary loves roses
- Source of the picture: wikipedia.org