Here are some examples of the various kinds of isolated singularities:

  1. removable: Consider f(z)=g(z)g(z0)zz0 for g an entire function. Then f has a removable singularity at 1;;z_0.
  2. Poles: f(z)=ezz3 has a pole of order 1;;3 at z=0. f(z)=ez1zz3 has a pole of order 1;;1 at z=0. In general, you can get an idea of the order of the poles by looking at the highest degree term in the principal part of the Laurant series.
  3. Essential Singularities: Some examples of essential singularities at 1;;z=0 are f(z)=sin(1z) and f(z)=e1/z.
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