What is the X in X-mas?
1640s, from French linéaire, from Latin linearis "belonging to a line," from linea "string, line" (see line (n.)). Essentially the same word as lineal; "in Latin linearis the original suffix -alis was dissimilated to -aris, but in Late Latin this rule was no longer productive and the formation or re-formation in -alis remained unchanged." [Barnhart]. Linear A and Linear B (1902-3) were names given to two related forms of linear Minoan writing discovered 1894-1901 in Crete by Sir Arthur Evans.
linear lin·e·ar (lĭn'ē-ər)
Of, relating to, or resembling a line; straight.
(Scientific computation) A property of a system whose output is not proportional to its input. For example, a transistor has a region of input voltages for which its output voltage is found by multiplying the input voltage by the gain of the transistor. Outside this region though, the transistor behaves non-linearly, meaning that it does not obey this simple equation. The behaviour of a system containing non-linear components is thus harder to model and to predict.