1.VerbContraction of might + have:
used to express the possibility of something occurring in the past as condition to another non-occurring past event
"If we had gone to Hollywood, we might've met a film star.; I think I might've left my umbrella on the train."
2.Verbused to express the possibility of something occurring in the past as condition to another non-occurring past event
"If we had gone to Hollywood, we might've met a film star."
3.Verbused to express uncertainty about a past event
"I think I might've left my umbrella on the train."