Are fissile isotopes and fissionable isotopes the same thing?

Question

If not, what are they exactly?

Answer 1

"Fissile" is distinguished from "fissionable". "Fissionable" are any materials with atoms that can undergo nuclear fission. "Fissile" is defined to be materials that are fissionable by neutrons with zero kinetic energy. "Fissile" thus, is more restrictive than "fissionable" — although all fissile materials are fissionable, not all fissionable materials are fissile. Some authorities even restrict the term fissionable to mean only non-fissile materials.

Answer 2

Fissile Isotopes