Nepal Bhasa (नेपाल भाषा, Nēpāl bhāṣā), also known as Newāh Bhāy (नेवा: भाय्), is one of the major languages of Nepal. It was Nepal's administrative and day-to-day language from the 14th to the late 18th centuries. Nepal Bhasa is spoken today as a mother tongue by the Newars, the indigenous inhabitants of Nepal Mandala, which consists of the Kathmandu Valley and surrounding regions.
Outside Nepal, it is spoken in India, particularly in Sikkim state where it is one of the 11 official languages. Nepal Bhasa is a Tibeto-Burman language, but it has been greatly influenced by Indo-Aryan languages.
Among the nearly 250 languages in this group, Nepal Bhasa is one of the only four with an old written tradition. Despite the high level of development, Newar culture and language are both under threat today. Nepal Bhasa has been listed as being "definitely endangered" by UNESCO. (Wikipedia)