Complementarity

Great economic complementarity, huge potential for cooperation in various fields, and a strong desire to cooperate open up broad prospects for us for the development of bilateral relations.

"Synergy is one of the most overused words in the English language, but there is a tremendous complementarity to these organizations."

For complementarity, there are entailments both from affirmative sentences to the corresponding negative sentences (which is what ordinary antonymy allows) and from negative sentences to the corresponding affirmative sentences. [...] That light is on entails That light is not off. That light is not on entails That light is off.