???? ???????? ????????? ???? ???? ?? ???The two most typical grammatical rules where this happens is when conjugating before or present tenses. For examples:?? ???? ??????, ???? ???? ???? ?? ??? ??????.???????? ???????? ????, ???????? ?????? ????????? ???????????? ???? ????.?? ???? ?????????????????????? ?? ????????????? ?? ??? ??(??)?????????? ???