What is Nonlinear?

Nonlinear definition and meaning on Dictionary terms:
of, consisting of, or using lines: linear design.
pertaining to or represented by lines: linear dimensions.
extended or arranged in a line: a linear series.
involving measurement in one dimension only; pertaining to length: linear measure.
of or relating to the characteristics of a work of art in which forms and rhythms are defined chiefly in terms of line.
having the form of or resembling a line: linear nebulae.

Mathematics. consisting of, involving, or describable by terms of the first degree.having the same effect on a sum as on each of the summands: a linear operation.

Electronics. delivering an output that is directly proportional to the input: a linear circuit; a linear amplifier.
threadlike; narrow and elongated: a linear leaf.