Set operations: (1) Union A ∪ B = all elements in A or B; (2) Intersection A ∩ B = elements in both A and B; (3) Complement A' or A^c = elements in U but not A; (4) Difference A - B = elements in A but not B; (5) Symmetric difference A Δ B = (A - B) ∪ (B - A). Example: A = {1,2,3}, B = {2,3,4}, U = {1,2,3,4,5}. A ∪ B = {1,2,3,4}; A ∩ B = {2,3}; A' = {4,5}; A - B = {1}; A Δ B = {1,4}. Formulas: |A ∪ B| = |A| + |B| - |A ∩ B|; |A - B| = |A| - |A ∩ B|. De Morgan's Laws: (A ∪ B)' = A' ∩ B'; (A ∩ B)' = A' ∪ B'. Exam tip: Use Venn diagrams for visualization. Understand operation notation clearly.