Generally speaking, a graph—usually a bar graph—of frequency distributions, in which the x-axis (horizontal) represents a series of definable quantities (such as, for example, a range of weights of members of a population), while the y-axis (vertical) represents how often those quantities occur in the sampled population. The actual data accumulated is represented as a series of rectangles, with bases equal to the division of definable quantities and heights that represent the frequency with which those quantities occur.

In color analysis, a histogram (also called a frequency histogram) is used to determine the distribution of colors in a scanned image. See Frequency Histogram.