 So-called "slender" consonants are palatalised while "broad" consonants are neutral or velarised.The vowels ' and ' are classified as slender, and ', ', and ' as broad.The spelling rule known as ' ("slender to slender and broad to broad") requires that a word-medial consonant or consonant group followed by a written ' or ' be also preceded by an ' or '; and similarly if followed by ', ' or ' be also preceded by an ', ', or '.