Bollywood (Hindi: बॉलीवुड, Urdu: بالی وڈ) is the informal name given to the popular Mumbai-based Hindi-language film industry in India. The term is often incorrectly used to refer to the whole of Indian cinema. Bollywood is only a part of the Indian film industry.
The name is a portmanteau of Bombay (the former name for Mumbai) and Hollywood, the center of the American film industry. Though some deplore the name, arguing that it makes the industry look like a poor cousin to Hollywood, it seems likely to persist and now has its own entry in the Oxford English Dictionary.
Bollywood is commonly referred to as Hindi cinema, even though Hindustani, the substratum common to both Hindi and Urdu, might be more accurate. Bollywood consists of the languages of Hindi, Urdu and English. The use of poetic Urdu words is fairly common. The connection between Hindi, Urdu, and Hindustani is an extremely contentious matter and is discussed at length in the linked articles relating specifically to the languages.
There has been a growing presence of Indian English in dialogue and songs as well. It is not uncommon to see films that feature dialogue with English words and phrases, even whole sentences. There is growing number of English films. A few films are also made in two or even three languages (either using subtitles, or several soundtracks).