\Lin"e*ar\ (-[-e]*[~e]r), a. [L. linearis, linearius, fr.
linea line: cf. F. lin['e]aire. See 3d {Line}.]
1. Of or pertaining to a line; consisting of lines; in a
   straight direction; lineal.
2. (Bot.) Like a line; narrow; of the same breadth
   throughout, except at the extremities; as, a linear leaf.
{Linear differential equation} (Math.), 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} (Math.), an equation of the first degree
   between two variables; -- so called because every such
   equation may be considered as representing a right line.
{Linear measure}, the measurement of length.
{Linear numbers} (Math.), 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 a square, the
   linear figure is called a root.
{Linear problem} (Geom.), a problem which may be solved
   geometrically by the use of right lines alone.
{Linear transformation} (Alg.), a change of variables where
   each variable is replaced by a function of the first
   degree in the new variable.