The Terai or Tarai is to a lowland region in parts of northern India and southern Nepal that lies to the south of the outer foothills of the Himalayas, the Sivalik Hills and north of the Indo-Gangetic Plain. This lowland belt is characterised by tall grasslands, scrub savannah, sal forests and clay rich swamps. In North India, the Terai spreads from the Yamuna River eastward across Haryana, Uttarakhand, Uttar Pradesh, Bihar and West Bengal. The Terai is part of the Terai-Duar savanna and grasslands ecoregion. Nepal's Terai stretches over 33,998.8 km2 (13,127.0 sq mi), about 23.1% of Nepal's land area, and lies at an elevation of between 67 and 300 m. The region comprises more than 50 wetlands. North of the Terai rises the Bhabar, a narrow but continuous belt of forest about 8–12 km (5.0–7.5 mi) wide.

Nepali is an Indo-Aryan language native to the Himalayas region of South Asia. It is the official, and most widely spoken, language of Nepal, where it also serves as a lingua franca. Nepali has official status in the Indian state of Sikkim and in the Gorkhaland Territorial Administration of West Bengal. It is spoken by about a quarter of Bhutan's population. Nepali also has a significant number of speakers in the states of Arunachal Pradesh, Assam, Himachal Pradesh, Manipur, Meghalaya, Mizoram and Uttarakhand. In Myanmar it is spoken by the Burmese Gurkhas. The Nepali diaspora in the Middle East, Brunei, Australia and worldwide also use the language. Nepali is spoken by approximately 19 million native speakers and another 14 million as a second language.