“Supralinear” means directly over a letter; “sublinear” means directly under a letter.
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.