n.先行；[物]进动；（分点）岁差
In the third chapter, precession cone semi-angle is discussed. 第三章主要讨论进动锥角的问题。
Spacecraft tracking could look for a similar precession of Mars's orbit. 利用追踪太空船，也可以找寻火星轨道类似的进动。
He then accounts for the precession of the equinoxes. 然后他解释分点岁差。
