linear
1 adj A linear process or development is one in which something changes or progresses straight from one stage to another, and has a starting point and an ending point.
...the linear view of time, with the idea that the past is moving into the present and the present into the future.
2 adj A linear shape or form consists of straight lines.
...the sharp, linear designs of the Seventies and Eighties.
3 adj Linear movement or force occurs in a straight line rather than in a curve.
non-linear , nonlinear
If you describe something as non-linear, 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. adj
(Antonym: linear)
...a non-linear narrative structure.