the abugida is not an alphasyllabary. However, most languages have words that are more complicated than a sequence of CV syllables, even ignoring tone. The first complication is syllables that consist of just a vowel (V). This issue does not arise in some languages because every syllable starts with a consonant. This is common in Semitic languages and in languages of mainland SE Asia; for such languages this issue need not arise. For some languages, a zero consonant letter is used as though every syllable began with a consonant. For other languages, each vowel has a separate letter that is used for each syllable consisting of just the vowel. These letters are known as independent vowels, and are found in most Indic scripts. These letters may be quite different from the corresponding diacritics, which by contrast are known as dependent vowels. As a result of the spread of writing systems, independent vowels may be used to represent syllables beginning with a glottal stop, even for non-initial syllables. The next two complications are sequences of consonants before a vowel (CCV) and syllables ending in a consonant (CVC). The simplest solution, which is not always available, is to break with the principle of writing words as a sequence of syllables and use a unit representing just a consonant (C). This unit may be represented with: a modification that explicitly indicates the lack of a vowel (virama), a lack of vowel marking (often with ambiguity between no vowel and a default inherent vowel), vowel marking for a short or neutral vowel such as schwa (with ambiguity between no vowel and that short or neutral vowel), or a visually unrelated letter. In a true abugida, the lack of distinctive marking may result from the diachronic loss of the inherent vowel, e.g. by syncope and apocope in Hindi. When not handled by decomposition into C + CV, CCV syllables are handled by combining the two consonants. In the Indic scripts, the earliest method was simply to arrange them vertically, but the two consonants may merge as a conjunct consonant letters, where two or more letters are graphically joined in a ligature, or otherwise change their shapes. Rarely, one of the consonants may be replaced by a gemination mark, e.g. the Gurmukhi addak. When they are arranged vertically, as in Burmese or Khmer, they are said to be 'stacked'. Often there has been a change to