The converse of discriminant validity. An aspect of construct validity, in which measures of constructs that theoretically should be related to each other are shown, in fact, to be related to each other (i.e., you should be able to show a correspondence or convergence between similar constructs). Thus, the operationalization of a hypothetical construct should converge on other operationalizations with which it shares theoretical similarities.
See Construct, Construct validity, Discriminant validity, External validity, Internal validity, Multitrait-multimethod matrix