Hindu ( pronunciation (help·info)) refers to an identity associated with the philosophical, religious and cultural systems that are indigenous to the Indian subcontinent. As used in the Constitution of India, the word "Hindu" is attributed to all persons professing any Indian religion (i.e. Hinduism, Jainism, Buddhism or Sikhism). In common use today, it refers to an adherent of Hinduism.
With more than a billion adherents, Hinduism is the world's third largest religion. The vast majority of Hindus, approximately 940 million, live in India. Other countries with large Hindu populations include Nepal, Bangladesh, Sri Lanka, Mauritius, Suriname, Guyana, Trinidad & Tobago, Fiji and the island of Bali
The demographics of India are inclusive of the second most populous country in the world, with over 1.21 billion people (2011 census), more than a sixth of the world's population. Already containing 17.5% of the world's population, India is projected to be the world's most populous country by 2025, surpassing China, its population reaching 1.6 billion by 2050. Its population growth rate is 1.41%, ranking 102nd in the world in 2010.
India has more than 50% of its population below the age of 25 and more than 65% below the age of 35. It is expected that, in 2020, the average age of an Indian will be 29 years, compared to 37 for China and 48 for Japan; and, by 2030, India's dependency ratio should be just over 0.4.
India has more than two thousand ethnic groups, and every major religion is represented, as are four major families of languages (Indo-European, Dravidian, Austroasiatic and Tibeto-Burman languages) as well as two language isolates (the Nihali language spoken in parts of Maharashtra and the Burushaski language spoken in parts of Jammu and Kashmir).