In linguistics, in the field of structural dialectology, a diasystem is a single genetic language which has two or more standard forms. Some dialects are often divided into separate languages due to different historical and cultural development. Other possible differences between languages include vocabulary, such as Occitan being affected by French and Catalan by Spanish words, and writing systems, such as Hindi in Devanagari and Urdu in the Arabic script, despite being mutually intelligible. Some languages are officially recognized as distinct despite having no barriers in speech, writing or lexicon, but are distinguished by legal and political factors, such as Catalan with Valencian. Thus, a diasystem can also be described as a single language that is spoken by two or more distinct communities.