pain threshold

threshold of suffering; point at which it is difficult to stand pain

The term pain threshold refers to the minimum intensity or duration of a sensory stimulus at which it becomes interpreted as painful. In scientific literature the term is clearly differentiated from the term pain tolerance. Pain threshold is the minimum stimulus which elicits pain and involves measurement of stimulus intensity, whereas pain tolerance is the degree of pain which a subject can tolerate, and involves a measurement of a subject's response to pain.
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Pain is an unpleasant feeling that is conveyed to the brain by sensory neurons. The discomfort signals actual or potential injury to [more]Pain threshold - Community and Resources

Noun
1. the lowest intensity of stimulation at which pain is experienced; "some people have much higher pain thresholds than do other people"
(hypernym) absolute threshold

The point at which a person becomes aware of pain.