A causal diagram is a graphical tool that enables the visualisation of causal

Causality

Causality is the relationship between an event and a second event , where the second event is understood as a consequence of the first....

 relationships between variables

Variable (mathematics)

In mathematics, a variable is a value that may change within the scope of a given problem or set of operations. In contrast, a constant is a value that remains unchanged, though often unknown or undetermined. The concepts of constants and variables are fundamental to many areas of mathematics and...

 in a causal model

Causal model

A causal model is an abstract model that describes the causal mechanisms of a system. The model must express more than correlation because correlation does not imply causation....

. A typical causal diagram will comprise a set of variables (or nodes) defined as being within the scope of the model being represented. Any variable in the diagram should be connected by an arrow to another variable with which it has a causal influence - the arrowhead delineates the direction of this causal relationship, e.g., an arrow connecting variables A and B with the arrowhead at B indicates a relationship whereby (all other factors being equal) a qualitative or quantitative change in A may cause change in B.