To speculate or assume that something happened in the past
When to use
Speculating about past events, Expressing uncertainty about past facts, Predicting past situations
The nuance
Attach -(았/었)을 것 to the past stem of verbs or adjectives to express speculation or assumption about past events. It means 'must have done' or 'probably did'. In conversation, '-았/었을 거예요' is common. It can also be used in negative sentences. For example, 갔을 것이다 = 갔었을 것, 가지 않았을 것이다 = 가지 않았었을 것.
