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i. Mary has three children
ii. Mary has exactly three children

What are the above sentences cases of: entailment or presupposition? Please explain thank you
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Entailment:
Sentence ii entails sentence i because if ii is true, i must be true, and if i is false, ii must be false.
Presupposition:
The person named Mary exists.

Google
entailment presupposition
and/or see http://www.msu.edu/course/lin/437/entpresu.htm

CJ
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so what you are saying is, it is both entailment and presupposition, as i'm aware this is possible for a sentence to be both.
Anonymousso what you are saying is, it is both entailment and presupposition, as i'm aware this is possible for a sentence to be both.
Generally speaking:

A presupposition may be contained within a single sentence.
Entailment is a relationship between two sentences.

CJ