The script encodes three vowels, "a", "i", "u", and twenty-two consonants, "k", "x", "g", "c", "ç", "j", "t", "θ", "d", "p", "f", "b", "n", "m", "y", "v", "r", "l", "s", "z", "š", and "h". Old Persian contains two sets of consonants: those whose shape depends on the following vowel and those whose shape is independent of the following vowel. The consonant symbols that depend on the following vowel act like the consonants in Devanagari. Vowel diacritics are added to these consonant symbols to change the inherent vowel or add length to the inherent vowel. However, the vowel symbols are usually still included so would be written as [di even though [di already implies the vowel. For the consonants whose shape does not depend on the following vowels, the vowel signs must be used after the consonant symbol.