?????? ???? ???????????? ?????? ????????????.The 2 most frequent grammatical rules where by this happens is when conjugating prior to now or existing tenses. For examples:- ???? ??: ??, ??, ??(??, ???????? ??), ??????, ??, ?????- ???? ?????????? ???? ???????? ?????????? ??????????? ????????. ?????????????????·????: ??· ?????? ????, ??·???? ??, ?