All 4 Uses

discern
in
Identical, by Ellen Hopkins
(Auto-generated)

Nope, no discernable spies.†
Chpt 3.

discernable = noticeable or understandable

standard suffix: The suffix "-able" means able to be. This is the same pattern you see in words like breakable, understandable, and comfortable.
For no discernible reason, my arms sprout goose bumps and my forehead leaks sweat.†
Chpt 12. *

discernible = possible to notice or understand
Still I croak, "Okay," look into his eyes, try to discern what's hiding there.†
Chpt 24.

discern = notice or understand something
I look right, left, over my shoulder, across the street, but can't discern a single person who might qualify as a spy.†
Chpt 24.

Definitions:

(1) (discern)
to notice or understand something -- often something that is not obvious
(2) (meaning too rare to warrant focus)