begun
v.v. the past participle of 'begin'. You use it with 'have' or 'has' to show that an action started in the past and is still happening or just finished.
v. the past participle of 'begin'. Used in perfect tenses and passive constructions to indicate the start of an action or state.
The movie has already begun.
By the time we arrived at the stadium, the match had already begun and the home team was leading.
The project, having begun under a different administration, faced significant structural challenges that required the new team to rethink their entire strategy from the ground up.
As a past participle, it must follow an auxiliary verb like 'have', 'has', or 'had'.
I begun the work yesterday.I began the work yesterday.Learners often confuse the past simple 'began' with the past participle 'begun'. Use 'began' for the simple past without an auxiliary verb.