'Dài kè' literally means 'to substitute for a class' — the character 代 (dài) means 'to replace or act on behalf of', and 课 (kè) means 'class' or 'lesson'. Together, they form a verb meaning to temporarily take over teaching duties for another teacher who is absent due to illness, leave, or other reasons. It's commonly used in school, university, and training contexts.

This term emphasizes the temporary, functional nature of the arrangement — the substitute teacher isn’t permanently assigned but fills a specific gap. While often used as a verb ('He will dài kè tomorrow'), it can also function as a noun in phrases like 'dài kè老师' (substitute teacher). The action implies responsibility, preparation, and alignment with the original lesson plan — not just showing up, but delivering instruction effectively.