lin·e·al 
(lĭnē-əl)
(lĭnē-əl)adj.
1. Belonging to or being in the direct line of descent from an ancestor.
2. Derived from or relating to a particular line of descent; hereditary.
3. Linear.
[Middle English, from Old French, from Late Latin līneālis, consisting of lines, from Latin līnea, line; see LINE1.]
line·al·ly adv.