diffraction region
Technical term used in physics and optics to describe the area where diffraction effects are significant.
In the diffraction region, the wave nature of light becomes prominent.
回折 means 'diffraction' itself, while 回折領域 refers specifically to the region or zone where diffraction occurs.
Compound of 回折 (diffraction) and 領域 (region, area). The exact historical derivation is uncertain, but the term is a straightforward technical compound.