The formal definitions given by Daniels and Bright for abugida and alphasyllabary differ; some writing systems are abugidas but not alphasyllabaries, and some are alphasyllabaries but not abugidas. An abugida is defined as "a type of writing system whose basic characters denote consonants followed by a particular vowel, and in which diacritics denote other vowels". (This 'particular vowel' is referred to as the "inherent" or "implicit" vowel, as opposed to the "explicit" vowels marked by the 'diacritics'.) An alphasyllabary is defined as "a type of writing system in which the vowels are denoted by subsidiary symbols not all of which occur in a linear order (with relation to the consonant symbols) that is congruent with their temporal order in speech". Bright did not require that an alphabet explicitly represent all vowels. ʼPhags-pa is an example of an abugida that is not an alphasyllabary, and modern Lao is an example of an alphasyllabary that is not an abugida, for its vowels are always explicit.