-tropy

1.
a combining form occurring in abstract nouns that correspond to adjectives ending in -tropic, or -tropous:
neurotropy.
Also, -tropism.
Origin
< Greek -tropia. See -trope, -y3
British Dictionary definitions for -tropy

-tropism

combining form
1.
indicating a tendency to turn or develop in response to a certain stimulus: phototropism
Word Origin
from Greek tropos a turn
-tropy in Medicine

-tropy suff.
The state of turning in a specified way or from a specified stimulus: thixotropy.