Causal notation

A causal notation is a notation to express cause and effect.

In nature and human societies, many phenomena have causal relationships where one phenomenon A (a cause) impacts another phenomenon B (an effect). Establishing causal relationships is the aim of many scientific studies across fields ranging from biology and physics to social sciences and economics. It is also a subject of accident analysis, and can be considered a prerequisite for effective policy making.

To describe causal relationships between phenomena, non-quantitative visual notations are common, such as arrows, e.g. in the nitrogen cycle or many chemistry and mathematics textbooks. Mathematical conventions are also used, such as plotting an independent variable on a horizontal axis and a dependent variable on a vertical axis, or the notation ${\displaystyle y=f(x)}$ to denote that a quantity "${\displaystyle y}$" is a dependent variable which is a function of an independent variable "${\displaystyle x}$". Causal relationships are also described using quantitative mathematical expressions.

The following examples illustrate various types of causal relationships. These are followed by different notations used to represent causal relationships.