When people talk about the meaning of one word (e.g. sheep) being “part of”, or “contained in”, the meaning of some other word (e.g. ewe), they are generally describing a lexical entailment. Strictly speaking, of course, entailment is a meaning relation between propositions or sentences, not words. When we speak of “lexical entailments”, we mean that the meaning relation between two words creates an entailment relation between sentences that contain those words. This is illustrated in (1–4). In each pair of sentences, the (a) sentence entails the (b) sentence because the meaning of the italicized word in the (b) sentence is part of, or is contained in, the meaning of the italicized word in the (a) sentence. We can say that ewe lexically entails sheep, assassinate lexically entails kill, etc.
(1) a. John assassinated the Mayor.
b. John killed the Mayor.
(2) a. John is a bachelor.
b. John is unmarried.
(3) a. John stole my bicycle.
b. John took my bicycle.
(4) a. Fido is a dog.
b. Fido is an animal.
These intuitive judgments about lexical entailments can be supported by additional linguistic evidence. Speakers of English feel sentences like (5), which explicitly describe the entailment relation, to be natural. Sentences like (6), however, which seem to cast doubt on the entailment relation, are unnatural or incoherent:3
(5) a. It can’t possibly be a dog and not an animal.
b. It’s a dog and therefore it’s an animal.
c. If it’s not an animal, then it follows that it’s not a dog.
(6) a. #It’s not an animal, but it’s just possible that it’s a dog.
b. #It’s a dog, so it might be an animal.
Cruse (1986: 12) mentions several additional tests for entailments which can be applied here, including the following:
(7) Denying the entailed component leads to contradiction:
a. #John killed the Mayor but the Mayor did not die.
b. #It’s a dog but it’s not an animal.
c. #John is a bachelor but he is happily married.
d. #The child fell upwards.
(8) Asserting the entailed component leads to unnatural redundancy (or pleonasm):
a. #It’s a dog and it’s an animal.
b. ⁇Kick it with one of your feet. (Cruse 1986: 12)
c. ⁇He was murdered illegally. (Cruse 1986: 12)
3 Examples from Cruse (1986: 14).
