Division into syllables is a difficult area, and different theories have been proposed. A widely accepted approach is the maximal onset principle: this states that, subject to certain constraints, any consonants in between vowels should be assigned to the following syllable. Thus the word "leaving" should be divided rather than *, and "hasty" is rather than * or *. However, when such a division results in an onset cluster which is not allowed in English, the division must respect this. Thus if the word "extra" were divided * the resulting onset of the second syllable would be , a cluster which does not occur initially in English. The division is therefore preferred. If assigning a consonant or consonants to the following syllable would result in the preceding syllable ending in an unreduced short vowel, this is avoided. Thus the word "comma" (in RP) should be divided and not *, even though the latter division gives the maximal onset to the following syllable.