When considering eigenstate order in MBL systems, one generally speaks of highly excited eigenstates at energy densities that would correspond to high or infinite temperatures if the system were able to thermalize. In a thermalizing system, the temperature is defined via T = ( d S d E ) − − 1 where the entropy S is maximized near the middle of the many-body spectrum (corresponding to T = ∞ ∞ ) and vanishes near the edges of the spectrum (corresponding to T = 0 ± ± ). Thus, "infinite temperature eigenstates" are those drawn from near the middle of the spectrum, and it more correct to refer to energy-densities rather than temperatures since temperature is only defined in equilibrium. In MBL systems, the suppression of thermal fluctuations means that the properties of highly excited eigenstates are similar, in many respects, to those of ground states of gapped local Hamiltonians. This enables various forms of ground state order to be promoted to finite energy densities.