Noun
English Wikipedia has an article on:Laurent seriesWikipedia
Laurent series (plural Laurent series)
A power series generalising Taylor series, in which the exponents may be positive or negative integers.
A Laurent series is thus any series of the form : If such a series converges, then in general it does so in an annulus rather than a disc, and possibly some boundary points. Source: Internet
One may define formal differentiation for formal Laurent series in a natural way (term-by-term). Source: Internet