Inorthography, azero consonant,silent initial, ornull-onset letter is a consonantletter that does not correspond to aconsonant sound, but is required when aword orsyllable starts with avowel (i.e. has anull onset). Someabjads,abugidas, andalphabets have zero consonants, generally because they have an orthographic rule that all syllables must begin with a consonant letter, whereas the language they transcribe allows syllables to start with a vowel. In a few cases, such asPahawh Hmong below, the lack of a consonant letter represents a specific consonant sound, so the lack of a consonant sound requires a distinct letter to disambiguate.
InArabic, the non-hamzated letter⟨ا⟩alif is often a placeholder for an initial vowel.
InJavanese script, the letter ꦲ ha is used for a vowel (silent 'h').
In Koreanhangul, the zero consonant isㅇ (이응)ieung. It appears twice in오이;oi, "cucumber".ㅇ also represents/ŋ/ -ng at the end of a syllable, but historically this was a distinct letter.
Burmeseအ,Khmer អ,Thai อ (อ อ่าง),Lao ອ (ອ ໂອ),Shan ဢ (ဢ ဢၢင်ႇ) are null-initial vowel-support letters. Thai อ่าง, for example, isang "basin". (า is the vowela and ง the consonantng.) อ and ອ pull double duty as vowels in some positions.
InThaana of the Maldives, އ is a zero. It requires a diacritic to indicate the associated vowel: އި isi, އޮo, etc. This is similar to an abjad, but the vowel mark is not optional.
TheLontara script for Buginese, with zero ᨕ, is similar to Thaana, except that without a vowel diacritic ᨕ represents an initial vowela. TheLepcha script of Nepal is similar.
In theCanadian Aboriginal syllabics, a triangle represents a vowel-initial syllable. The orientation of this triangle specifies the vowel: ᐁe, ᐃi, ᐅo, ᐊa.
In theRomanized Popular Alphabet used forHmong, anapostrophe marks a vowel-initial syllable. The absence of any letter indicates that the syllable starts with a glottal stop, a far more common occurrence.
Pahawh Hmong, asemi-syllabary, also has a zero consonant, as well as a letter for glottal stop, with the lack of an initial consonant letter indicating that the syllable begins with a/k/.
Virama, azero-vowel diacritic in many abugidas, such as HindiDevanagari. The virama marks the absence of a vowel; the absence of a virama or vowel diacritic implies an inherent vowel such as/a/.
Sukun, the optional zero-vowel diacritic of Arabic.
