User blog comment:TristanLambert/The Extension Function/@comment-25601061-20180619033021/@comment-35435096-20180720220336

I consider an extension a number that has been extended from a previous function. For example FOST was extended to FOOT which made the number much larger. So FOST would = Ext(0) and FOOT would = Ext(1). This new function takes uncomputable Numbers and makes lots extensions to them using new and different functions each time.