What do historians call a relationship in which one event or variable

contributes to the occurrence of another?

Causality

Explanation:

Causality or as it called as cause-effect relationship between the two events. It refers to the occurrence of an event which is the result of another event. There can be so many factors causing an event which are causal factors and which lie in the past and they partially result in the occurrence of another event which lies in the future. Therefore it explains the process of progression which is based on logic and other basic concepts.