"Most Bose-Einstein condensates of atomic gases have internal degrees of freedom originating from the spin. ... When a Bose-Einstein condensate is trapped in a magnetic potential, the spin aligns along the direction of a local magnetic field, and the internal degrees of freedom are virtually frozen. The condensate is therefore described by a scalar order parameter. When it is trapped in an optical potential, the internal degrees of freedom are liberated because the optical potential exerts the same force on an atom irrespective of which magnetic sublevel it is in. Such a condensate is called a spinor Bose-Einstein condensate; the order parameter of this condensate has 2ƒ+1 components, where ƒ is the hyperfine spin for alkali atoms and the electronic spin for chromium."