effect (result of an action) / effect / effect

sound effect (artificially created or enhanced sound)

(ecology) greenhouse effect (process by which a planet is warmed by its atmosphere)

domino effect (chain of events)

side effect (an adverse effect)

butterfly effect (technical notion of sensitive dependence on initial conditions in chaos theory)

(film, television) special effect (effect that cannot be reasonably achieved by normal means)

Mozart effect (supposed phenomenon by which listening to Mozart induces improvement in mental performance)

(ecology) Allee effect (negative population growth observed at low population densities)

(physics) Doppler effect (change in frequency or wavelength of a wave due to relative motion of the observer)