In four-dimensional Minkowski spacetime, extended supersymmetry has more than one independent Weyl spinor supercharge, together with their adjoints. The index distinguishes these supercharges.
A full four-dimensional hypermultiplet is a matter supermultiplet equivalent to two chiral superfields in conjugate gauge group representations. Pseudoreal representations can admit half-hypermultiplets; these do not provide genuinely complex chiral gauge spectra.