Legal definitions of an autonomous body, private body and non government organisation.and

Dear Sir, The Government issued a circular for protecting the pay of teachers specifically to attract the talent that exists in non-government organisation (NGOs) with a condition that the organisation must be an autonomous Body. The circular does not mention anything like Central / State autonomous bodies in the circular. Appreciate if you can clarify the legal definition of An Autonomous Body and Non -Government organisation for better understanding. I shall like to know whether 1) Organizations established under Registered Society-registered under the Societies Registration Act XXI of 1860 will legally qualify under this circular. 2) An organisation which has got SIRO status from DSIR – GOI will be eligible or not. 3) Legal definition of a Private Body which has not registered even as a Society, in reference to an Autonomous Body. Appreciate, an early response giving some examples of Autonomous Bodies where no grant comes from the Government. However, these organization will be following some norms of the Govt. department. An early response along with some links/references which clarifies the subject matter at your earliest.