echo-, ech-

(Greek: sound, noise; especially a returned sound; repetition, imitation)

Characteristic of echolalia; that is, habitual or pathological repetition of words or remarks made by others.
echolocation (s) (noun), echolocations (pl)
echopathy (s) (noun), echopathies (pl)
The pathological repetition through imitation of the actions or speech of another; a form of psychopathology: Echopathy occurs most frequently in the catatonic phase of schizophrenia when the patient assumes the postures, gestures, and speech of another individual in what appears to be "mirror fashion" behavior.
The mental association of sound tones, or certain sounds, with particular colors.
A disorder of speech where there is an involuntary repetition several times of the same word.
echopraxia (s), echopraxias (pl) (nouns)
The uncontrolled repetitions or imitations of the actions of another person: "Echopraxia is a synonym of echomimia which is the imitation of the motions of other people or excessive movements, and/or repeating what others say or do; especially, excessive motor activities, Tourette syndrome (involuntary movements), schizophrenia (psychotic disorder characterized by delusions and hallucinations), and other neurologic diseases."
An instrument for intensifying sounds produced by percussion of the thorax.

The term percussion in medicine normally refers to the act of tapping or striking the surface of the body in order to learn the condition of the parts by the sound emitted or the sensation imparted to the fingers.