+**E0** denotes a fundamental or ground state within various systems. It often signifies the initial energy level, a base reference point, or a system's undisturbed condition, preceding any [Change](/wiki/change) or [Interaction](/wiki/interaction).
+## See also
+- [Ground State](/wiki/ground_state)
+- [Reference Point](/wiki/reference_point)
+- [System State](/wiki/system_state)
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