Silent vav

The silent vāv occurs only in words of Iranian origin, and is not present in any Turkic or Arabic loanwords that entered the language. Words in Middle Persian containing the labialized voiceless velar fricative [xʷ] preceding a long vowel developed such that the sound underwent delabialization and simply became the voiceless velar fricative [x]. In cases where it preceded the short near-open front unrounded vowel [æ] it delabialized and took on the sound of the close-mid back rounded vowel [o], evolving from [xʷæ] to [xo]. Despite this, the written language continues to reflect the old standards of pronunciation, hence the silent vāv remains written. These linguistic evolutions did not take place in certain areas of Greater Iran, and thus certain dialects do not have the silent vāv as a feature.[6][7]

Historically, sometimes poetic usages of the silent vāv did not follow the traditional literary rules and guidelines.[8][4] This can be seen in the following poem by Sa'adi in his Bustan book:[9]

Phonetic transcription:

[moxænˈnæs kʰe biːˈdɒːd bæɾ xæd ˈkʰonæd]
[æz ɒːn be kʰe bɒː diːˈɡæɾiː bæd ˈkʰonæd]

According to the Persian literary rules, خود should be pronounced as [xod]; however, as is visible in this poem, it atypically takes on the sound of [xæd] and rhymes with بد/[bæd] in the verse following it. This silent vāv taking on the Fathe/Zebar sound of [æ] rather than [o] of Zamme/Pish is a very common feature in classical Persian poetry, also seen, for example, in the works of Ferdowsi and Nezami.[8][4][10]

Historically, the silent vāv was marked in some manuscripts by replacing the خ in the خو combination with the 3-dotted variant, څ, to form څو. This is no longer a feature of Persian orthography in any manner, with the modified letter څ having no presence in the modern alphabet.[11]