A linear function is a mathematical relationship between two variables that can be represented by a straight line on a graph. It is typically expressed in the form of an equation, such as y = mx + b, where m is the slope of the line, indicating its steepness, and b is the y-intercept, which shows where the line crosses the y-axis. In a linear function, changes in one variable result in proportional changes in the other. This means that if you increase or decrease the input value (x), the output value (y) will change at a constant rate. Linear functions are commonly used in various fields, including economics, science, and engineering, to model relationships between quantities.