The inverse with respect to addition; the opposite.
A consequent of a contrary.
An incompatible substance; one of a group of things that cannot be placed or used together because of a change of chemical composition or opposing medicinal qualities.
Of two things: that cannot coexist; not congruous because of differences; unable to function together due to dissimilarities.
Incapable of being together without mutual reaction or decomposition, as certain medicines.