D defs.my
Entry 3 senses Webster, 1913

Linear

/(lĭn"ē̇*ẽr)/ · Lin·e·ar · IPA /ˈlɪni.əɹ/
01 a. Of or pertaining to a line; consisting of lines; in a straight direction; lineal.
  1. 1.
    Of or pertaining to a line; consisting of lines; in a straight direction; lineal.
  2. 2.
    Like a line; narrow; of the same breadth throughout, except at the extremities; as, a linear leaf.(Bot.)
  3. 3.
    Thinking in a step-by-step analytical and logical fashion; contrasted with holistic, i.e. thinking in terms of complex interrelated patterns; as, linear thinkers.
    Linear thinkers concluded that by taking the world apart, the actions of people were more predictable and controllable.” — David Morris (Conference presentation, Fairfield University, October 31, 1997)
Phrases & compounds
Linear differential equation — an equation which is of the first degree, when the expression which is equated to zero is regarded as a function of the dependent variable and its differential coefficients.
Linear equation — an equation of the first degree between two variables; -- so called because every such equation may be considered as representing a right line.<-- = straight line! -->
Linear measure — the measurement of length.
Linear numbers — such numbers as have relation to length only: such is a number which represents one side of a plane figure. If the plane figure is square, the linear figure is called a root.
Linear problem — a problem which may be solved geometrically by the use of right lines alone.
Linear transformation — a change of variables where each variable is replaced by a function of the first degree in the new variable.