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In symbolic logic, the universal quantifier ∀ indicates "for every" or "for all." For example, ∀ x A, p(x) means for all x belonging to A, the proposition p is valid. The existential quantifier ∃ indicates "there exists." So, for instance, ∃ x A, p(x) means there exists at least one x, belonging in A, for which the proposition p(x) is valid.

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