Question: is begun a proper word?
Answer: The word 'begun' is the past participle of 'begin'. 'Begun' is used in the perfect tense sentences. It is, therefore, incorrect to write 'I begun', as 'begun' can never be used without an auxiliary verb ('has', 'have' or 'had'). ... When combined with 'has', 'begun' is part of the past perfect tense.