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The meaning of a sentence, what a sentence expresses. However, sentences and propositions are not the same thing. Different sentences can express the same proposition, and the same sentence can express different propositions.

Example of one sentence that may express more than one proposition: "I am here." If it is uttered by Joe then it will express one proposition, if it is uttered by Janellle then it will express another. Or, if Joe utters it while at the Eiffel tower vs. at the local garbage dump, then they will express different propositions.

Example of two sentences that express the same proposition: 1) Janelle is the female sibling of Scott. 2) Janelle is Scott's sister.