?????? ??????????????????? ?? ??????? ???????? ??? ???????????? ???? ???? ????? ?????? ????????? ??The 2 commonest grammatical rules exactly where this happens is when conjugating in the past or present tenses. For illustrations:?? ???? ??????, ????????????, ???? ???? (???????? ??)???????? ???????????? ?? ??? ?????? ???? ??????????? ????? ???? ????