A linear function is a function whose graph is a straight line. Such a function can be used. to describe variables that change at a constant rate. For example, the following table shows the accumulation of snow on the morning of a. snowstorm: Time 6:00 am 8:00 am 10:00 am 12:00 pm. Snow depth 2 in. 5 in. 8 in. 11 in.