What’s the difference in meaning between the following pairs of words?

Whats the meaning of sound?

• Answer:

  sound is just vibrations through the air. For transverse waves the displacement of the medium is perpendicular to the direction of propagation of the wave. A ripple on a pond and a wave on a string are easily visualized transverse waves. In longitudinal waves the displacement of the medium is parallel to the propagation of the wave. A wave in a "slinky" is a good visualization. Sound waves in air are longitudinal waves. compression is a higher than normal air-pressure, rarefaction is lower than normal air-pressure. together these two elements make up a sound wave, which is what we hear when something is hit or played. if you look at any normal visual representation of a soundwave, the humps above the middle line are called compression, the humps below, rarefaction.