  The spin of a composite particle, like a nucleus or a hadron, is generated by
the composition of angular moments (consisting of spins and orbital angular
moments) of the constituents. The composition of two angular moments is done by
the standard way with the use of Clebsch-Gordan coefficients. However, if there
are more than two constituents, the composition must be done in a hierarchical
way, which admits more ways leading to the same resulting spin state |J,
J_{z}>. Different composition patterns can generate states with the same spin
quantum numbers, but which may vary in the contributions of different kinds of
the constituents. We will discuss which composition patterns could be preferred
in the hadrons from the viewpoint of minimal energy of the bound system. In
this context, particular attention is paid to the role of gluons or quark
orbital angular momentum in the proton spin.
