PREFIX
conter - against, opposite
in - in, into, not
inter - between
re - back, again

ROOT
act - do, drive
aud/audi - hear

SUFFIX
-ence - state, quality, act
-ible - able to be
-ion - state, quality, act

WORDS AND DEFINITIONS
counteract - to act directly against; to prevent from affection
interaction - communication between two or more things
reaction - a response
audience - a group of listeners or spectators
inaudible - unable to be heard