What is referred to when discussing the correlation between two variables?

When discussing the correlation between two variables, the term bivariate correlation is used. This concept focuses specifically on the statistical relationship between two distinct variables, examining how they vary together. In a bivariate correlation analysis, the goal is to determine whether an increase in one variable is associated with an increase or decrease in another variable, and the strength and direction of that relationship are often quantified using a correlation coefficient, such as Pearson's r.

Univariate correlation refers to the analysis involving only one variable, focusing on its distribution and characteristics without comparing it to another variable, which does not fit the context of correlating two variables. Multivariate correlation involves analyzing more than two variables simultaneously, aiming to understand the relationships among them in a more complex manner, which extends beyond simple bivariate analysis. Partial correlation, on the other hand, examines the relationship between two variables while controlling for the effect of one or more additional variables, providing insights that are more nuanced than the primary relationship itself.

Thus, bivariate correlation specifically addresses the interaction between two variables and is the appropriate term for this discussion.