The text book used in one of my courses talks about expanding functions in powers of 1/z aka negative powers of z. The problem is that I cannot recall that any previous course taught me/challenged me on how to expand functions in negative powers. For example, Taylor series only have positive powers. Is there a general method of expanding in negative powers, like for Taylor series, or are there at best similar methods for similar functions? I fear I have overlooked something elementary here, because I feel strangely clueless about this one (and Internet searches have made me no wiser). The textbook only gives examples of the results of expansion in 1/z, but never gives any details on how it is done.