a. 同方向的

Synclastic \Syn*clas"tic\, a. [Pref. syn- + Gr. kla^n to break.]
(Math. Physics)
Curved toward the same side in all directions; -- said of
surfaces which in all directions around any point bend away
from a tangent plane toward the same side, as the surface of
a sphere; -- opposed to anticlastic. --Sir W. Thomson.