Os"cil*late (?), v. i. [imp. & p. p. Oscillated (?); p. pr. & vb. n. Oscillating (?).] [L. oscillare to swing, fr. oscillum a swing, a little mask or puppet made to be hung from trees and swing in the wind, prob. orig., a little mouth, a dim. from os mouth. See Oral, and cf. Osculate.]

1. To move backward and forward; to vibrate like a pendulum; to swing; to sway.

2. To vary or fluctuate between fixed limits; to act or move in a fickle or fluctuating manner; to change repeatedly, back and forth.

The amount of superior families oscillates rather than changes, that is, it fluctuates within fixed limits.
Dc Quincey.