either φ or ψ φ ∨ ψ ≃ ¬ (¬ φ ∧ ¬ ψ) at least 1 true—not both false	▿	not both φ and ψ ¬ (φ ∧ ψ) ≃ ¬ φ ∨ ¬ ψ not both true—at least 1 false
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both φ and ψ φ ∧ ψ ≃ ¬ (¬ φ ∨ ¬ ψ) both true—neither false	▵	neither φ nor ψ ¬ (φ ∨ ψ) ≃ ¬ φ ∧ ¬ ψ neither true—both false