Definition of "ascertainable"

For example, when regulation prevents a developer from building rental property, the value of existing or reasonably ascertainable leases represents an opportunity cost of the prohibition to the developer.

1990, Harold N. Skelton, “Houses on the Sand: Takings Issues Surrounding Statutory Restrictions on the Use of Oceanfront Property”, in Boston College Environmental Affairs Law Review, volume 18, number 1, page 144

The easily ascertainable fact, they point out, is that what they feel is not anger toward parents speaking Lennon's name, but only contempt for the few so ignorant of cultural history that they think it was John Lennon, instead of Paul McCartney, who sang "Why Don't We Do It in the Road?"

1991 March 23, Russell Baker, “Facing the Music”, in The New York Times‎, page 23

The real responsibility, the reasons behind the assassination, were still in dispute half a century later. But even events that are less crucial are still often incompletely ascertainable.

1991, Robert Conquest, “A Letter to a Soviet Historian”, in Academic Questions, volume 4, number 4, page 38