[1] The population of India was counted as 438,936,918 people.
[2] The 1961 census recognized 1,652 mother tongues, counting all declarations made by any individual at the time when the census was conducted.
[2] However, the declaring individuals often mixed names of languages with those of dialects, sub-dialects and dialect clusters or even castes, professions, religions, localities, regions, countries and nationalities.
[2] The list therefore includes "languages" with barely a few individual speakers as well as 530 unclassified "mother tongues" and more than 100 idioms that are non-native to India, including linguistically unspecific demonyms such as "African", "Canadian" or "Belgian".
[2] Modifications were done by bringing in two additional components- place of birth i.e. village or town and duration of stay (if born elsewhere).