If you describe something as nonlinear, you mean that it does not progress or develop smoothly from one stage to the next in a logical way. Instead, it makes sudden changes, or seems to develop in different directions at the same time.
Environmental systems tend to be nonlinear, and therefore not easy to predict.
nonlinear in British English
(nɒnˈlɪnɪə)
adjective
1.
not of, in, along, or relating to a line
2.
denoting digital editing in which edits are saved on computer, rather than videotape, thus enabling further edits to be made