to grasp (often fig.); to master; to know well; to understand sth well and know how to use it; fluency; to control; to seize (initiative, opportunity, destiny)[cedict]
在
zàiㄗㄞˋ
(located) at; (to be) in; to exist; in the middle of doing sth; (indicating an action in progress)[cedict]
on; on top; upon; first (of two parts); previous or last (week etc); upper; higher; above; previous; to climb; to go into; above; to go up; to attend (class or university); third tone of putonghua[cedict]