(Or alignment chart; also called nomograph, nomographic chart.) The graphical representation of an equation of three variables (, , ) = 0, by means of three graphical scales (not necessarily straight), arranged in such a manner that any straight line, called an index line, cuts the scales in values of , , and satisfying the equation. By introducing auxiliary variables and constructing auxiliary scales, equations containing more than three variables may also be represented by nomograms.
A computational aid consisting of two or more scales drawn and arranged so that the results of calculations may be found by the linear connection of points on them. Historically, it was used for calculating economic lot sizes or sample sizes for work measurement observations. Also called an alignment chart.