law: Transfer of Property Act, 1882
  54. "Sale" defined
  "Sale" is a transfer of ownership in exchange for a
  
  price paid or promised or part-paid and part-promised.
  Sale how made : Such transfer, in the case of tangible
  
  immovable property of the value of one hundred rupees and upwards, or in the
  
  case of a reversion or other intangible thing, can be made only by a registered
  
  instrument.
  In the case of tangible immovable property of a value less than
  
  one hundred rupees, such transfer may be made either by a registered instrument
  
  or by delivery of the property.
  Delivery of tangible immovable property takes place when the
  
  seller places the buyer, or such person as he directs, in possession of the
  
  property.
  Contract for sale: A contract for the sale of immovable
  
  property is a contract that a sale of such property shall take place on terms
  
  settled between the parties.
  It does not, of itself, create any interest in or charge on such
  
  property.