Diglossia is the occurrence of two distinct varieties of a language. For instance, the most common is a “high” variety, which is taught at school, used in the media, at church, and at scholarly gatherings, and a “low” variety, which is used in informal settings, such as friendly conversations or at home. However, the definition does not stop here. In some languages, such as Persian and Arabic, the difference between the classical or written and the spoken variations may be considered a form of diglossia. In this site, we often refer to diglossia as formal or informal or colloquial.

Diglossia in Persian has certain basic rules. Some of these rules are observed by almost all speakers, while others are used in different levels, depending on who the speaker is. First, consider:

As a general feature in Persian, also shared by many other Iranian dialects, in most cases an /ā/ followed by the alveolar nasal /n/ becomes a long /u/ ([ān] > [un]):

In a limited number of words /ā/ before the bilabial nasal /m/ also becomes /u/, such as: