Definition of "lineal"

lineal

/ˈlɪni.əl/

adjective
not comparable
1. Having an ancestral relationship to mothers, fathers, grandparents, (etc.) and having a descendant relationship to sons, daughters, grandchildren (etc.), exclusive of collateral siblings.
  Quotations
  the prime and ancient right of lineal succession
  1689 December (indicated as 1690), [John Locke], chapter 1, in Two Treatises of Government: […], London: […] Awnsham Churchill, […]
2. Inheriting by direct descent; having the right by direct descent to succeed (to).
  Quotations
  Oh that your Brows my Laurel had ſuſtain'd, / Well had I been depos'd, if You had Reign'd! / The Father had deſcended for the Son; / For only you are lineal to the Throne.
  1693 (first performance), John Dryden, “To My Dear Friend Mr. Congreve, on His Comedy, Call’d, The Double-Dealer”, in The Double-Dealer. A Comedy, London: […] Jacob Tonson […], published 1735, Act I
3. Composed of lines; delineated.
4. In the direction of a line; of a line; of or relating to a line; measured on, or ascertained by, a line; linear.