If you have ever looked at buying a flat or gone through a project brochure, you must have come across the terms FSI and Fungible FSI. They sound so technical that most people ignore them. But these two things decide how tall a building can be, how many flats it will have, and how much usable space you actually get. 

https://www.proclee.com/blog/fsi-and-fungible-fsi-in-real-estate-what-these-terms-really-mean