different between perceivable vs appreciable

English

perceive +? -able

perceivable (comparative more perceivable, superlative most perceivable)

Capable of being perceived; discernible.
- 1818, Jane Austen, Northanger Abbey, ch. 5,
  Every search for him was equally unsuccessful, in morning lounges or evening assemblies; neither at the Upper nor Lower Rooms, at dressed or undressed balls, was he perceivable.
- 2003, "Man in Pakistan: I'm on list," USA Today, 1 Jan. (retrieved 2 Nov. 2008),
  The only perceivable difference between the AP and FBI photos is that the man in the FBI photo is clean-shaven and shorter-haired.

From French appréciable.

appreciable (comparative more appreciable, superlative most appreciable)

Large enough to be estimated; perceptible; considerable.
- 2002, John J. Mearsheimer, "Realism, the Real World, and the Academy," in Realism and Institutionalism in International Studies (M. Brecher and F. P. Harvey, eds.), ?ISBN, p. 27:
  If NEAsia were a zone of peace, those American forces would be unnecessary and they could be sent home and demobilized, saving the U.S. taxpayer an appreciable sum of money.

appreciable in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913.

Send