Sensitivity

n. ability to perceive sensation; responsiveness; delicateness, state of requiring special treatment or care; susceptibility to outside influences; quality of being temperamental

Sensitivity may refer to: Sensitivity (biology)Sensitivity (electronics)Sensitivity (human)Sensitivity (information)Sensitivity (tests, medicine)Sensitivity (radio receiver)For sensitivity in finance, see beta coefficient and Greeks (finance)"Sensitivity" is also a song by R&B singer, Ralph Tresvant.
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Noun
1. (physiology) responsiveness to external stimuli; "sensitivity to pain"
(synonym) sensitiveness, sensibility
(hypernym) sense, sensation, sentience, sentiency, sensory faculty
(hyponym) hypersensitivity
(classification) physiology
2. the ability to respond to physical stimuli or to register small physical amounts or differences; "a galvanometer of extreme sensitivity"
(hypernym) physical property
(hyponym) frequency response
(attribute) sensitive
3. sensitivity to emotional feelings (of self and others)
(synonym) sensitiveness
(hypernym) feeling
(hyponym) oversensitiveness
(attribute) sensitive
4. susceptibility to a pathogen
(synonym) predisposition
(hypernym) susceptibility, susceptibleness
(hyponym) habitus
(attribute) sensitizing, sensitising
5. the ability to respond to affective changes in your interpersonal environment
(synonym) sensitiveness
(antonym) insensitivity, insensitiveness
(hypernym) ability
(hyponym) antenna, feeler

(n.)
The quality or state of being sensitive; -- used chiefly in science and the arts; as, the sensitivity of iodized silver.
  

When referring to a medical test, sensitivity refers to the percentage of people who test positive for a specific disease among a group of people who have the disease. No test has 100% sensitivity because some people who have the disease will test negative for it (false negatives).