A (macroscopic) classical state is due to the decoherence of quantum states of a lot of particles.
A quantum state is a quantum eigenstate or a superposition of quantum eigenstates.
a classical state = a macroscopic definite state
a quantum eigenstate = a microscopic definite state
a definite state = a state whose measurement result can be predicted with 100% certainty
— Me@2013.06.16
2013.06.17 Monday (c) All rights reserved by ACHK