they are three form for plural in arabic 1- جمع المذكر السالم it's for tow or more male and 2- جمع المؤنث السالم
it's for female 3- جموع التكسير
and that it's similar irregular form in english
and third is Complex because they are more 21 rules for it even people arabian don't know most of this rules but they are not so important