The phrase "substantial fraction" means a significant portion or part of something. It refers to a sizable or significant amount, but not necessarily the whole or majority. Full definition
Second, retail investors are buying substantial fractions of these offerings. (inc.com)
Indeed, in hot countries nearly every meat - based recipe calls for at least one spice, and most include many spices, especially the potent spices, whereas in cooler counties substantial fractions of dishes are prepared without spices, or with just a few.» (fieryfoodscentral.com)
Cracking driven by daily and seasonal temperature changes may help explain substantial fraction of sunny - day rockfalls (sciencemag.org)