一旦 (yīdàn) is used to express what would happen after a certain condition is met. Usually it is used with 就. This grammar pattern expresses that "once" one thing happens, "then" something else will happen.
Structure
一旦 + Condition，Subj. + 就 + Consequence
Keywords
一旦 · 就
Used for
Indicating cause and effect · Indicating conditions
Summary, structure, classification, and adapted sentence examples draw from the AllSet Learning Chinese Grammar Wiki under CC BY-NC-SA 3.0; changes were made. This noncommercial reference is based on an October 2023 snapshot.