不可或缺

The state of being absent from a place or event where one is expected to be, such as a class, meeting, or ceremony.

Abstract.

In an abstract manner; conceptually.

Profound; abstruse; recondite.

Academic; scholarly; relating to education and scholarship.

Academic; characterized by formal study or research.

Academic conference; a formal meeting for academic discussions.

Exchange of ideas, information, and research among scholars.

A periodical publication containing scholarly articles.

Academic affairs office; department handling educational administration.