The 15 main languages in India are :

Hindi : The most important Indian language, although it is only spoken as a mother tongue by about 20% of the population- mainly in the area known as the Hindi-belt, the cow-belt or Bimaru – Bihar, Madhya Pradesh, Rajasthan and Uttar Pradesh. This Indic language is the official language of the government, as well as of the states already mentioned, plus Haryana and Himachal Pradesh.
Assamese State language of Assam, and spoken by nearly 60% of that state’s population. Dated back to the 13th century.
Bengali spoken by nearly 200 million people (mostly in what is now Bangladesh), and the state language of West Bengal. Developed as a language in the 13th century.
Gujarati State language of Gujrat, Indic.
Kannada State language of Karnataka, spoken by about 65% of that state’s population.
Kashimiri Kashmiri speakers account for about 55% of the population of Jammu & Kashmir. It is an Indic language written in the Perso-Arabic script.
Malayalam A Dravidian language, it is the state language of Kerala.
Marathi An Indic language dating back to around the 13th century, Marathi is the state language of Maharashtra.
Oriya Another Indic language, it is the state language of Orissa where it is spoken by 87% of the population.
Punjabi Also Indic, it is the state language of Punjba. Although based on the same script as Hindi (Devanagari), it is written in a 16th-century script, known as Gurumukhi, which was created by the Sikh guru, Guru Angad.
Sanskrit one of the oldest languages in the world, and the language of classical India. All the Vedas and classical literature such as the Mahabharata and the Ramayana were written in this Indic language.
Sindhi a significant number of Sindhi speakers are found in what is now Pakistan, although the greater number are in India, In Pakistan the language is written in a Perso-Arabic script, while in India it uses the Devanagari script.
Tamil An ancient Dravidian language at least 2000 years old, and the state language of Tamil Nadu. It is spoken by at least 65 million people.
Telugu The Dravidian language spoken by the largest number of people, it is the state language of Andhra Pradesh.
Urdu Urdu is the state language of Jammu & Kashmir. Along with Hindi it evolved in early Delhi. While Hindi was largely adopted by the Hindi population, the Muslims embraced Urdu, and so the latter is written in the Perso-Arabic script and includes many Persian words.

Recently there have been moves to have
Konkani, a language spoken by many in the Goa area, Manipuri and Nepali (Gorkhali) recognised under the constitution.