by dialect, due to Dari having 8 distinct vowels compared to the 6 vowels of Iranian Persian. See Persian Phonology In Iranian Persian, none of these short vowels may be the initial or final grapheme in an isolated word, although they may appear in the final position as an inflection, when the word is part of a noun group. In a word that starts with a vowel, the first grapheme is a silent which carries the short vowel, e.g. (, meaning "hope"). In a word that ends with a vowel, letters , and respectively become the proxy letters for , and , e.g. (, meaning "new") or (, meaning "package"). Tanvin (nunation) Nunation (, ) is the addition of one of three vowel diacritics to a noun or adjective to indicate that the word ends in an alveolar nasal sound without the addition of the letter nun. Tašdid Other characters The following are not actual letters but different orthographical shapes for letters, a ligature in the case of the . As to (hamza), it has only one graphical form since it is never tied to a preceding or following letter. However, it is sometimes 'seated' on a , or , and in that case, the seat behaves like an ordinary , or respectively. Technically, hamza is not a letter but a diacritic. Although at first glance, they may seem similar, there are many differences in the way the different languages use the alphabets. For example, similar words are written differently in Persian and Arabic, as they are used differently. Novel letters The Persian alphabet has four extra letters that are not in the Arabic alphabet: , (ch in chair), (s in measure), . Deviations from the Arabic script Persian uses the Eastern Arabic numerals, but the shapes of the digits 'four' (), 'five' (), and 'six' () are different from the shapes used in Arabic. All the digits also have different codepoints in Unicode: * However, the Arabic variant continues to be used in its traditional style in the Nile Valley, similarly as it is used in Persian and Ottoman Turkish. Comparison of different numerals Word boundaries Typically, words are separated from each other by a space. Certain morphemes (such as the plural ending '-hâ'), however, are written without a space. On a computer, they are separated from the word using the zero-width non-joiner. Cyrillic Persian alphabet in Tajikistan As