The space of spin states therefore is a discrete degree of freedom consisting of three states, the same as the number of components of a vector in three-dimensional space. Quantum superpositions of these states can be taken such that they transform under rotations just like the spatial components of a rotating vector (the so-called 3 representation of SU(2)). If the vector boson is taken to be the quantum of a field, the field is a vector field, hence the name.