The placement of the "-" (or "" in the Japanese text) indicates where the stem of the vowel is. In other words, for a consonant-stem verb (i.e., the quadrigrade and N- and R-irregular classes), the final vowel is not considered part of the verb's root, so it is separated. However, for vowel-stem verbs (i.e., the upper and lower monograde and bigrade and K- ad S-irregular), the final vowel is considered part of the stem, except in the forms beginning in ("u"), because these reflect an ancient contraction of the final vowel of the verb with that ending. The K- and S-irregular classes are also special in this regard, because they are believed to be derived from vowel-stem verbs originally, but were subject to ancient contractions that caused them to lose their final vowel in all forms, and so their final vowels are no longer considered part of their roots (and are thus separated from them), even though they are considered vowel-stem verbs.