1. (used with a singular verb) Physics. the branch of physics that deals with sound and sound waves.
  2. (used with a plural verb) the qualities or characteristics of a room, auditorium, stadium, etc., that determine the audibility or fidelity of sounds in it.

adjective Also a·cous·ti·cal.

  1. pertaining to the sense or organs of hearing, to sound, or to the science of sound.
  2. (of a building material) designed for controlling sound.
  3. Music.
    1. of, relating to, or being a musical instrument whose sound is not electrically enhanced or modified.
    2. arranged for or made up of such instruments: an acoustic solo; an acoustic group.


  1. Obsolete. a remedy for deafness or imperfect hearing.


  1. (functioning as singular) the scientific study of sound and sound waves
  2. (functioning as plural) the characteristics of a room, auditorium, etc, that determine the fidelity with which sound can be heard within it


  1. of or related to sound, the sense of hearing, or acoustics
  2. designed to respond to, absorb, or control soundan acoustic tile
  3. (of a musical instrument or recording) without electronic amplificationan acoustic bass; an acoustic guitar

1680s, “science of sound,” from acoustic (also see -ics). Meaning “acoustic properties” of a building, etc., attested from 1885.


c.1600, from French acoustique, from Greek akoustikos “pertaining to hearing,” from akoustos “heard, audible,” verbal adjective from akouein “to hear,” probably from copulative prefix a- + koein “to mark, perceive, hear,” from PIE *kous- “to hear,” perhaps from root *(s)keu- “to notice, observe” (see caveat). Acoustic guitar (as opposed to electric) attested by 1958. Related: Acoustical; acoustically.


  1. The scientific study of sound, especially of its generation, transmission, and reception.


  1. Of or relating to sound, the sense of hearing, or the perception of sound.

  1. Used with a singular verb The scientific study of sound and its transmission.
  2. Used with a plural verb The total effect of sound, especially as produced in an enclosed space.
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