Susceptibility, n.; pl. Susceptibilities.
Etymology: [Cf. F. susceptibilité.]
1. The state or quality of being susceptible; the capability of receiving impressions, or of being affected.
2. Specifically, capacity for deep feeling or emotional excitement; sensibility, in its broadest acceptation; impressibility; sensitiveness. Magnetic susceptibility (Physics), the intensity of magnetization of a body placed in a uniform megnetic field of unit strength. Sir W. Thomson.
Syn. -- Capability; sensibility; feeling; emotion.
Shades of meaning
Fernald has no entry of its own for susceptibility; he lists it under power, sensibility.
Where he writes about it:
Sensitiveness denotes an especial delicacy of sensibility, ready to be excited by the slightest cause, as displayed, for instance, in the "sensitive-plant." Susceptibility is rather a capacity to take up, receive, and, as it were, to contain feeling, so that a person of great susceptibility is capable of being not only readily but deeply moved; sensitiveness is more superficial, susceptibility more pervading. — from sensibility
Thus, in physics, the sensitiveness of a magnetic needle is the ease with which it may be deflected, as by another magnet; its susceptibility is the degree to which it can be magnetized by a given magnetic force or the amount of magnetism it will hold. — from sensibility
So a person of great sensitiveness is quickly and keenly affected by any external influence, as by music, pathos, or ridicule, while a person of great susceptibility is not only touched, but moved to his inmost soul. — from sensibility