characteristic curve

:  the graphic curve or the graph picturing it that shows the relation between two variables a characteristic curve plotting the variations of grid potential and plate current in the normal operation of a vacuum tube the patient's fever chart showed the characteristic curve for the disease: a :  the curve indicating the variation of density in a developed photographic image that results from the increase of exposure expressed logarithmically —called also H and D curve, sensitometric curve b :  a curve showing the relationship between frequency and recording intensity or frequency and reproducing intensity in sound recording