The compressed regions and the space-out regions in longitude wave are refers to as

The correct answer is Compression and Rarefaction. When a longitudinal wave travels through a medium, it causes particles in the medium to oscillate back and forth parallel to the direction of wave propagation. The compressed regions are the areas where the particles are pushed closer together than their normal positions, while the rarefaction regions are the areas where the particles are spread apart more than their normal positions. These compressed and rarefied regions are collectively known as compression and rarefaction, respectively. For example, when sound waves travel through air, the compressed regions correspond to the high-pressure regions (peaks) of the sound wave, while the rarefaction regions correspond to the low-pressure regions (troughs) of the sound wave.