Q: Classify singularities at 0: sin z/z, 1/z², e^(1/z). sin z/z: limit = 1: REMOVABLE (define f(0) = 1!)! 1/z²: |f| → ∞: POLE of order 2! e^(1/z): Laurent Σ1/(n!zⁿ) - infinite principal part: ESSENTIAL! (Casorati-Weierstrass: dense image near essential!)