  Spin textures, i.e., the distribution of spin polarization vectors in
reciprocal space, exhibit diverse patterns determined by symmetry constraints,
resulting in a variety of spintronic phenomena. Here, we propose a universal
theory to comprehensively describe the nature of spin textures by incorporating
three symmetry flavors of reciprocal wavevector, atomic orbital and atomic
site. Such approach enables us to establish a complete classification of spin
textures constrained by the little co-group and predict unprecedentedly
reported spin texture types, such as Zeeman-type spin splitting in
antiferromagnets and quadratic spin texture. To examine the impact of atomic
orbitals and sites, we predict orbital-dependent spin texture and anisotropic
spin-momentum-site locking effects and corresponding material candidates
validated through first-principles calculations. Our theory not only covers all
possible spin textures in crystal solids described by magnetic space groups,
but also introduces new possibilities for designing innovative spin textures by
the coupling of multiple degrees of freedom.
