Hinduism () is an umbrella term for a range of Indian religious and spiritual traditions (sampradayas) that are unified by adherence to Dharma, a cosmic order maintained by its followers through rituals and righteous living, as expounded in the Vedas. The word Hindu originated as an exonym, and while Hinduism has been called the oldest surviving religion in the world, it is also described since the 19th century by the term Sanātana Dharma (lit. 'eternal dharma'). Vaidika Dharma (lit. 'Vedic dharma') and Arya Dharma are historical endonyms for Hinduism.
Hinduism entails diverse systems of thought, marked by a range of shared concepts that discuss theology, mythology, and other topics in textual sources. Hindu texts have been classified into Śruti (lit. 'heard') and Smṛti (lit. 'remembered'). The major Hindu scriptures are the Vedas, the Upanishads, the Puranas, the Ramayana, the Mahabharata (including the Bhagavad Gita), and the Agamas. Prominent themes in Hindu beliefs include karma (action, intent and consequences), saṃsāra (the cycle of death and rebirth) and the four Puruṣārthas, proper goals or aims of human life, namely: dharma (ethics/duties), artha (prosperity/work), kama (desires/passions) and moksha (liberation/emancipation from passions and ultimately saṃsāra). Hindu religious practices include devotion (bhakti), worship (puja), sacrificial rites (yajna), meditation (dhyana), and Yoga. Hinduism has no central doctrinal authority and many Hindus do not claim to belong to any denomination. However, scholarly studies recognise four major denominations: Vaishnavism, Shaivism, Shaktism and Smartism. The six Āstika schools of Hindu philosophy that recognise the authority of the Vedas are: Sankhya, Yoga, Nyaya, Vaisheshika, Mīmāṃsā, and Vedanta.
While the traditional Itihasa-Purana and its derived Epic-Puranic chronology present Hinduism as a tradition existing for thousands of years, scholars regard Hinduism as a fusion or synthesis of Brahmanical orthopraxy with various Indian cultures, having diverse roots and no specific founder. This Hindu synthesis emerged after the Vedic period, between c. 500 to 200 BCE, and c. 300 CE, in the period of the second urbanisation and the early classical period of Hinduism when the epics and the first Purānas were composed. It flourished in the medieval period, with the decline of Buddhism in India. Since the 19th century, modern Hinduism, influenced by Western culture, has acquired a great appeal in the West, notably reflected in the popularisation of Yoga and various sects such as Transcendental Meditation and the ISKCON's Hare Krishna movement.
Hinduism is the world's third-largest religion and considered the largest ethnic religion, with approximately 1.17 billion followers, or around 15% of the global population, known as Hindus, largely in India, Nepal, Mauritius, and in Bali, Indonesia. Significant numbers of Hindu communities are found in the countries of South Asia, in Southeast Asia, in the Caribbean, Middle East, North America, Europe, Oceania, Africa, and Australia.
The word Hindū is an exonym, derived from the Sanskrit word Sindhu, the name of the Indus River as well as the country of the lower Indus basin (Sindh).
The Proto-Iranian sound change *s > h occurred between 850 and 600 BCE.
"Hindu" occurs in Avesta as heptahindu, equivalent to Rigvedic sapta sindhu.
The 6th-century BCE inscription of Darius I mentions Hindush (referring to Sindh) among his provinces.
Hindustan (spelt "hndstn") is found in a Sasanian inscription from the 3rd century CE.
The term Hindu in these ancient records is a geographical term and did not refer to a religion. In Arabic texts, "Hind", a derivative of Persian "Hindu", was used to refer to the land beyond the Indus and therefore, all the people in that land were "Hindus", according to historian Romila Thapar.
By the 13th century, Hindustan emerged as a popular alternative name of India or northern India.
Among the earliest known records of 'Hindu' with connotations of religion may be in the 7th-century CE Chinese text Record of the Western Regions by Xuanzang. In the 14th century, 'Hindu' appeared in several texts in Persian, Sanskrit and Prakrit within India, and subsequently in vernacular languages, often in comparative contexts to contrast them with Muslims or "Turks". Examples include the 14th-century Persian text Futuhu's-salatin by 'Abd al-Malik Isami,
Jain texts such as Vividha Tirtha Kalpa and Vidyatilaka,
circa 1400 Apabhramsa text Kīrttilatā by Vidyapati, 16–18th century Bengali Gaudiya Vaishnava texts, etc.
These native usages of "Hindu" were borrowed from Persian, and they did not always have a religious connotation, but they often did.
In Indian texts, Hindu Dharma ("Hindu religion") was often used to refer to Hinduism.
Starting in the 17th century, European merchants and colonists adopted "Hindu" (often with the English spelling "Hindoo") to refer to residents of India as a religious community.
The term got increasingly associated with the practices of Brahmins, who were also referred to as "Gentiles" and "Gentoos".