Final answer:
A linear function is defined as a function that graphically represents a straight line on a graph and algebraically has a constant rate of change, expressed through the equation y = mx + b.
Step-by-step explanation:
The best definition of a is a function that is straight on a graph and has a constant rate of change. A linear equation typically takes the form y = mx + b, where m represents the slope, or the constant rate of change, and b represents the y-intercept, which is where the line crosses the y-axis (when x = 0). The constancy of the slope means that the function increases or decreases by the same amount for every one-unit change in the independent variable (x), thus the graph of a linear function is always a straight line.