the relation that exists when opposites cannot coexist | contradictoriness; |

opposition between two conflicting forces or ideas | contradiction; |

a contradiction of ideas that serves as the determining factor in their interaction | dialectic; |

the relation between propositions that cannot both be true at the same time | incompatibility; inconsistency; mutual exclusiveness; repugnance; |

exact opposition | contrary; |

the relation between contraries | contrariety; |

some third thing similar to two opposites but distinct from both | tertium quid; |

a relation of direct opposition | contrary; opposite; reverse; |

something inverted in sequence or character or effect | inverse; opposite; |

a relational difference between states; especially between states before and after some event | change; |

a significant change | difference; |

a graded change in the magnitude of some physical quantity or dimension | gradient; |

a gradient in concentration of a solute as a function of distance through a solution | concentration gradient; |

a gradient in the gravitational forces acting on different parts of a nonspherical object | gravity gradient; |

change in temperature as a function of distance (especially altitude) | temperature gradient; |

a logical relation between propositions p and q of the form `if p then q'; if p is true then q cannot be false | conditional relation; implication; logical implication; |

the relation between opposing principles or forces or factors | antagonism; |