perceptible

definition: 
(Especially of a slight movement or change of state) able to be seen or noticed:
sentence: 
The alteration of the fork due to heat is scarcely perceptible, but wind instruments, and particularly the organ, rise almost proportionately to the increase in temperature of the surrounding air, because sound travels at an enhanced rate as the temperature rises.
These changes were already perceptible before the war .
difficulty: 
easy
toefl frequency: 
3
toefl classification: