The past stem of a verb is used to construct the forms of the preterit and the imperfect as well as the past participle.
The past stem is formed by cutting off the ن an ending.
The past stem is always regular:
"to give" داد - دادن
" to receive" رسید - رسیدن
"to bring" آورد - آوردن
"to buy" خرید - خریدن
"to be" بود - بودن
See Also: