"Fly" is an irregular verb. Its past tense is "flew" and its past participle is "flown."
"Began" is an irregular verb. Its past tense form does not follow the usual pattern of adding "-ed" to the base form of the verb.
regular or irregular
It's an irregular verb.
It's an irregular verb.
irregular
Regular Verb
It's an irregular verb.
To swim is an irregular verb.
It's irregular.
It's an irregular verb.
It's an irregular verb.