Synergism is the act of combining two or more agents, substances, systems, organizations and their properties so that they cooperate or interact to create a combined effect that is greater than the sum of their separate effects. Synergism is a term used to describe only cooperation that results in positive effects or a harmony of the two elements to create a larger effect.
Safeopedia Explains Synergism
Synergism cannot be used to describe combinations of elements that to not work in harmony with one another and cause effects that are less than or the same as the sum of the combined effects of both elements. The opposing antonyms for synergism, therefore, include words such as disunity, divorce, disagreement, division, hostility, handicap etc..