The quality or state of being sensitive; sensitiveness.

(biology) The noun "sensitivity" refers to the ability of an organism or organ to respond to external stimuli, and can also describe the vulnerability of a pathogen to medical treatment.

(statistics) The probability, in a binary classification test, of a true positive being correctly identified.

(electronics) The degree of response of an instrument to a change in an input signal.

(photography) The degree of response of a film etc. to light of a specified wavelength.