The status of Romani
A common misconception in popular reference to the language of the Roma is that there are multiple "Gypsy languages" or "Roma languages". This plural reference is erroneous. It is based on lumping together two different populations: the community of Romani speakers, most of whom have been settled in their respective regions for the past 4-5 centuries or even longer, some of whom however have migrated between European regions in certain historical periods over the past two-three centuries; and the diverse populations of Travellers.
The latter, the various Traveller communities, generally have no linguistic features in common. Some, however, have their own individual speech forms. These usually consist of a distinct but small vocabulary, usually up to 500 words that are occasionally inserted into conversation in the dominant or majority language. They are usually referred to by linguists as 'special lexicons'. Examples are the special vocabulary of the Jenisch Travellers in Germany, Switzerland, and Austria, the special in-group vocabulary of the Irish Travellers (called 'Cant' or 'Gammon', and in some publications 'Shelta'), and that of the Woonwagenbewoners in the Netherlands and Belgium (called 'Bargoens'). There is no historical connection between these individual vocabularies, and they are generally not similar to one another. While it is acknowledged and appreciated that users of such special vocabularies regard them as tokens of their respective group-identity and heritage, and often refer to them as 'languages', it must be emphasised that special lexicons are fundamentally different from the ordinary concept of what a 'language' is, since they serve only particular conversational functions, and since they consist primarily of a limited set of distinct vocabulary and have no distinct grammatical structures at all.
By contrast, the Romani language is a fully-fledged language which possesses its own extensive everyday lexicon as well as grammar and sound system. It is a distinct and coherent language by any measure. Lexicon, grammar, and sounds are, as in most European languages, subject to geographical variation, but historically speaking this variation is young, having emerged only over the past 600-500 years. The various dialects or varieties of Romani derive from a single ancestor idiom, and the differences among them resemble to a considerable extent the kind of differences found among dialects of major European languages such as Italian or German.