Definitions of sensitivity:

• noun:   the ability to respond to affective changes in your interpersonal environment
• noun:   the ability to respond to physical stimuli or to register small physical amounts or differences

  Example: "A galvanometer of extreme sensitivity"

• noun:   (physiology) responsiveness to external stimuli

  Example: "Sensitivity to pain"

• noun:   sensitivity to emotional feelings (of self and others)
• noun:   susceptibility to a pathogen