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1) of, relating to, or used in diagnosis
2) using the methods of or yielding a diagnosis <a \diagnostic service> <\diagnostic properties>
di·ag·nos·ti·cal·ly -ti-k(ə-)lē adv
diagnostic n the art or practice of diagnosis often used in pl.
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di·ag·nos·tic (di″əg-nosґtik) pertaining to or subserving diagnosis; distinctive of or serving as a criterion of a disease, as signs and symptoms.Medical dictionary. 2011.