Definitions for

**"Linear relationship"**A situation in which the best-fitting regression line is a straight line.

A relationship between two variables that can be described by a straight line. Non-linear relationships can often be linearised by the application of a transformation (e.g. a logarithmic transformation).

When two variables are considered together, the first increases as the second increases (or decreases), so that, when plotted graphically, a straight line results.