= Microstate
{wiki}
A <microstate> is a complete microscopic specification within the chosen model. For two distinguishable, noninteracting <two-level systems>, label the units $A,B$ and their states $0,1$, with <energies> $0,\Delta$ and $\Delta>0$. The four <microstates> are
$$
(0,0),\quad(0,1),\quad(1,0),\quad(1,1),
$$
with total <energies> $0,\Delta,\Delta,2\Delta$. Distinguishability matters: $(0,1)$ and $(1,0)$ describe different assignments to the labeled units. Noninteraction matters too: their <energies> add without an extra coupling term.
For a classical particle model, a <microstate> can instead be a point in <phase space>, specifying every <position> and <momentum>. In the quantum <canonical ensemble>, the sum uses <energy eigenstates>; a general <quantum state> may also contain <quantum coherence>, which an <energy> label alone does not specify.
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