reciprocal of There are frequently two ways to state the same thing: we can say 'spermatocyte lacks asters' or 'asters absent from spermatocyte'. In this case the quality is 'lacking all parts of type' - it is a (relational) quality of the spermatocyte, and it is with respect to instances of 'aster'. One of the popular requirements of PATO is that it continue to support 'absent', so we need to relate statements which use this quality to the 'lacking all parts of type' quality. q1 reciprocal_of q2 if and only if : q1 and q2 are relational qualities and a phenotype e q1 e2 mutually implies a phenotype e2 q2 e.