The non-greeting twitches my lips into a weak smile.

We can imagine that the Δ points in [Δ] are drawn clockwisely on a circle of circumference Δ, in the order 0, 1, 2, …, Δ − 1, such that every two adjacent points have distance 1 on the circle.

a monarchically-governed society

Binocular torsion can be transformed into cyclovergence and cycloversion. Cyclovergence is the difference of the torsion of the left and right eyes; cycloversion is the mean of the left and right eye torsion.