In mathematics, basic hypergeometric series, or q-hypergeometric series, are q-analogue generalizations of generalized hypergeometric series, and are in turn generalized by elliptic hypergeometric series. A series xn is called hypergeometric if the ratio of successive terms xn+1/xn is a rational function of n. If the ratio of successive terms is a rational function of qn, then the series is called a basic hypergeometric series. The number q is called the base.
The basic hypergeometric series 2 ϕ 1 ( q α , q β ; q γ ; q , x ) {\displaystyle {}_{2}\phi _{1}(q^{\alpha },q^{\beta };q^{\gamma };q,x)} was first considered by Eduard Heine (1846). It becomes the hypergeometric series F ( α , β ; γ ; x ) {\displaystyle F(\alpha ,\beta ;\gamma ;x)} in the limit when base q = 1 {\displaystyle q=1} .