Romanian stands out from its sister Romance languages through the conditions of its historical evolution. It has developed in isolation from the other Romance languages, and in cultural and linguistic contact with various non-Romance populations. The history of writing in Romanian, and the earliest preserved texts, dating from the 16th century, also reflect this rather unique heritage. The main dialectal division is marked geographically by the Danube river. The variety developed north of the Danube forms the Daco-Romanian group, while the variety developed south of the Danube includes Aromanian and Megleno-Romanian. The most characteristic changes affecting consonants in the development of Romanian include several patterns of palatalization (with or without affrication, depending on the segments’ place and manner of articulation), the emergence of labial-coronal clusters as part of a more general preference for labials, and rhotacism, a major feature of nonstandard varieties. Major vocalic changes include patterns of diphthongization, vowel raising before nasals and in the context of trills, which led to the development of two phonemic central vowels, /ɨ/ and /ʌ/. Many of these patterns show variation among different varieties. In all varieties of Romanian, vowel alternations are involved in morpho-phonological alternations. The stress pattern of modern Romanian follows the stress pattern of Balkan Romance. The standard and nonstandard varieties differ with respect to their intonation patterns, particularly in the case of yes/no questions.