?????? ?? ?? ?? ???? ???????????? ??????????The 2 most typical grammatical principles where this happens is when conjugating in past times or present tenses. For examples:- ???? ??: ??, ??, ??(??, ???????? ??), ??????, ??, ???????????(??)??: ???????? ???????????? ??·???????(???????? ???????????, ??????, ???????? ?????? ????), ????????(??????????