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Logic Symbols — Complete Index
This page covers propositional logic, predicate logic, modal logic, and proof theory. Essential for computer science, mathematics, and philosophy.
1) Propositional Logic
| Symbol | Meaning |
|---|---|
| ¬ | negation |
| ∧ | and |
| ∨ | or |
| → | implies |
| ↔ | equivalence |
| ⊕ | exclusive-or |
2) Predicate Logic
| Symbol | Meaning |
|---|---|
| ∀ | Universal quantifier |
| ∃ | Existential quantifier |
| ∃! | Unique existence |
| ∄ | Not exists |
3) Modal Logic
| Symbol | Meaning |
|---|---|
| □ | Necessarily |
| ◇ | Possibly |
4) Inference & Proof
| Symbol | Meaning |
|---|---|
| ∴ | therefore |
| ∵ | because |
| ⊢ | syntactic entailment |
| ⊨ | semantic entailment |
| ∎ | QED (end of proof) |