Romani and Romanes are the general names for the language and its many different variants used by Roma, Sinti, Kale and all other ethnic groups in Europe who speak or spoke an Indic, or respectively Indo-Aryan language. The term 'Romanes', derived from an adverb, is used almost exclusively in German speaking countries. The term 'Romani' is derived from an adjective: 'Romani čhib' - ‘Roma-tongue, Roma-language’. Romani, often spelled Romany in English texts, is used internationally as the general term for Romani language and its different variants or dialects.

Source:
Factsheets on Roma, Permalink