Statistical Glossary
Specificity:
Specificity (of a medical diagnostic test for a disease) is the probability that the test will come out negative for a person without the disease.
Specificity itself is not sufficient to characterize a test. For example, a test reporting all subjects who take the test as "negative" (not having the disease) has 100% specificity, but such a "test" is useless - because it has 0% sensitivity.